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meena Lt LO NAL CHEMICAL SERIES 
H. P. TALBOT, Pu. D., Consuutina Epitror 


EXPERIMENTAL 
ORGANIC CHEMISTRY 


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EXPERIMENTAL 
ORGANIC CHEMISTRY 


BY 
JAMES ie NORRIS, seue: 


PROFESSOR OF CHEMISTRY IN VANDERBILT UNIVERSITY 
6é 


First Epirron 


McGRAW-HILL BOOK COMPANY, Inc. 
239 WEST 39TH STREET, NEW YORK 
6 BOUVERIE STREET, LONDON, E. C. 
1915 





PREFACE 


This book is designed primarily to be used as a laboratory 
guide in connection with courses in organic chemistry in which 
the student follows in the laboratory the subject as developed 
in the class-room. An attempt has been made to furnish direc- 
tions for experiments to illustrate the methods of preparation and 
the chemical properties of the more important classes of organic 
compounds. As a consequence, the student following the work 
as given, comes in contact with many substances of importance 
which are not handled by one whose laboratory work consists 
solely in the preparation of a few compounds. For example, 
directions are given in considerable detail for experiments 
which illustrate the properties of fatty amines, hydroxy acids, 
carbohydrates, fats, proteins, etc., subjects which receive scant, 
if any, attention in many laboratory courses in organic chemistry. 

Directions for a large number of preparations are also given. 
These serve to illustrate the more important synthetic methods 
and the different kinds of laboratory technique with which the 
student should become acquainted. In connection with the 
directions for the preparation of typical compounds, experiments 
are given which illustrate the properties of the compounds made. 
These experiments include in each case a study of the reactions 
of the substance which are of particular value in the identification 
of the characteristic group present. 

No attempt has been made to introduce novel preparations; 
the ones given are, in the main, those commonly used. These 
have been selected on account of their simplicity and the fact 
that they illustrate the principles to be taught; they are as novel 
to the student as any that could be devised. Although the older 
preparations are used, the laboratory details are, in many cases, 
different from those commonly employed. The changes have 
been the result of a detailed study of the preparations which, 
in many cases, resulted in simplification and improvement. A 
few new preparations are described; these are to illustrate, in 
most cases, the properties of compounds that have not been stud- 
ied commonly in laboratory courses in organic chemistry. 

Vv 


v1 PREFACE 


A feature of the book is the introduction of directions for the 
preparation of certain compounds on a very small seale. Stu- 
dents often acquire the habit of careless work in the laboratory 
practice in organic chemistry. Preparation-work on the small 
scale serves to counteract this effect and to develop a technique 
that is valuable. Such work is often necessary in the identifica- 
tion of unknown compounds when a small amount only of the 
substance is available. In many cases a crystalline derivative 
whose melting-point can be determined, can be prepared in a 
pure condition from but two or three drops of a substance. 
Among the examples of work of this kind which are given are the 
preparation of acetanilide from acetic acid, glyceryl tribenzoate 
from glycerol, dinitrobenzene from benzene, and dibenzalacetone 
from acetone. In order to facilitate such work, a section in the 
first chapter is devoted to a consideration of the technique used 
in the manipulation of small quantities of substances. 

The final chapter of the book deals with the methods used to 
identify organic compounds by a study of their chemical behavior 
and physical properties. The method is outlined only, since the 
pedagogical value of the work depends largely upon giving the 
student opportunity to apply the knowledge he has gained 
throughout the course in the study of the behavior of the typical 
classes of organic compounds. It has been the experience of 
the author for a number of years, that laboratory practice of this 
kind undertaken at the end of the course, is of great value to the 
student, on account of the fact that it gives him an opportunity 
to review, correlate, and apply many of the facts he has learned. 
The practical application of his knowledge is evident. When a 
student has been able to identify definitely a number of com- 
pounds which were unknown to him, he feels that he has gained 
power in handling problems in organic chemistry. 

A chapter of the book is devoted to detailed directions for 
carrying out the simpler operations used in laboratory work in 
organic chemistry. In order that the student may make use of 
this information when it is necessary, references are given through- 
out the book to the paragraph and page where the particular 
process to be employed is described. It is impossible to repeat — 
in the laboratory directions details for these processes, and if the 
student does not have these details before him he is apt to carry . 


PREFACE vil 


out the operation in a careless manner. It is believed that a 
definite reference to the place where the process is described may 
be useful. 

The book contains directions for more work than can be done 
in a laboratory course of the usual length. An opportunity is 
thus given the teacher to select the work that is best adapted to 
the needs of his students. The method of numbering and letter- 
ing the experiments makes it possible to assign readily the work 
to be done by the class. 

The author has consulted all the well-known texts on labora- 
tory work in organic chemistry in the preparation of the book. 
In writing the directions for the preparation of compounds on 
a small scale, valuable help was obtained from 8. P. Mulliken’s 
“The Identification of Pure Organic Compounds.” A number 
of experiments on fats, carbohydrates, and proteins have been 
adapted, with the permission of the author, from a laboratory 
manual in descriptive organic chemistry prepared for the use of 
students of household economics, by Professor Alice F. Blood, of 
Simmons College. The author wishes to express his thanks for 
the courtesy shown in granting permission to make use of this 
material. 

All the figures in the book were prepared from drawings made 
by the wife of the author; for this help and for assistance in read- 
ing the proof he is deeply grateful. 

The author will be pleased to have called to his attention any 
mistakes which may be discovered by those who use the book; 
any suggestions as to improved directions for the experiments 
will also be gladly received. 

JAMES F’, Norris. 





CONTENTS 


PaGs 
PREFACE . Vv 
CHAPTER I.—Lasoratory METHODS. 


General directions, 1—Crystallization, raul gL AIT ca ie 
traction, 20—Sublimation, 23—Drying agents, 24—Use of reflux 
condenser, 25—Manipulation of sodium, 27—Manipulation of 
small quantities of substances, 28—Determination of physical 
properties, 31—Qualitative analysis, 38. 


CHAPTER II.—Generrat Processes: HyprocaRBONS Of THE 
METHANE SERIES. ies 
Methane, 43—Ethane, Hee Te ieariyl Bee Carseene san eatplines 
46. 


CHAPTER III.—Unsatruratep HypRocARBONS. . 
Ethylene, 49—Amylene, 50—Acetylene, 51. 


CHAPTER IV.—A.tcono.s . : i Spe PINAR Spe A TR ie chad. 
Methyl alcohol, 538—Ethyl oH OL 53—Allyl alcohol, 58— 
Glycerol, 59. 


CHAPTER V.—Acips . : 
Formic acid, 61—Acetic AGEL Boson, ielesbaclnn tb 66. 


CHAPTER VI.—ErTuHErs, Esters, AND ANHYDRIDES. ; Sa 
Ether, 69—Isoamyl-ethyl ether, 72—Acetic eae 73— 
Baseinic anhydride, 74—Potassium ethyl sulphate, 75—Ethyl 
acetate, 76—Isoamy]l acetate, 78—Fats and oils, 78. 


CHAPTER VII.—A.LpDEHYDES AND KETONES . 
Formaldehyde, 81—Acetaldehyde, 82—-Acetone, 84. 


CHAPTER VIII.—AmInEs AND AMIDES . ; 
Methylamine, 86—Lecithin, 88—Acetamide, ee iea: 90. 


CHAPTER IX.—CYANOGEN AND RELATED COMPOUNDS 
Cyanogen, 92—Potassium cyanide, 92—Potassium ferercraniiel 
93—Potassium ferricyanide, 93—Methyl cyanide, 94—Iso- 
' eyanides, 95. 
. ix 


42 


49 


53 


61 


69 


81 


86 


92 


x CONTENTS 


PaGE 
CHAPTER X.—HaALocen CoMPounDs. . . . 96 
Methyl iodide, 96—Ethyl bromide, 97—Ethyl Sodides 99- Taos 
amyl bromide, 100—Chloroform, 101—Ethylene bromide, 103— 
Acetyl chloride, 105. 


CHAPTER XI.—Compounps ContTarmntna Two UNLIKE SUBSTITU- 
ENTSe.te . 106 
Trichloracetic pet 0G stneke Ate 106——Tarkania ‘aniee 107— 
Citric acid, 109—Acetoacetic ester, 110—Chloral, 113. 


CHAPTER XII.—C rBonypDRATES . .. . 45) ee 
Dextrose, 114—General reactions of ie sugars, 115=Snerua 
117—Lactose, 117—Starches, 119—Dextrin, 122—Cellulose, 122— 
Pentosans, 124. 


CHAPTER XIII.—Compounps ConrTAINING SULPHUR. ...... 125 
Mercaptan, 125—Thiocyanates, 125—Xanthates, 125. 


CHAPTER XIV.—Uric Acip AND RELATED Compounpbs. .... . 126 
Uric acid, 126—Caffeine, 127. 


CHAPTER XV.—ARomatic HyDROCARBONS . . . 128 
Benzene, 128—Ethylbenzene, 130__Diphenyimernanal 132 —"Heva- 
Phenyiciene: 133—Naphthalene, 133- 


CHAPTER XVI.—Nirro Compounps anp SutpHonic Acs . . . .135 
Nitrobenzene, 135—m-Dinitrobenzene, 137—Sodium  benzene- 
sulphonate, 138—Benzenesulphonyl chloride, 140—Benzenesul- 
phonamide, 141—p-Toluenesulphonic acid, 141. 


CHAPTER XVII.—Hatogen Derivatives or Aromatic HypRo- 
CARBONS. .. . . 143 
Brombenzene, 149 Dsbrombeneenes 144 Pennine i halaeee 
compounds, 144—Triphenylchlormethane, 146. 


CHAPTER XVIII.—Aromatic AMINES . . . eee 
Aniline, 148—Methylaniline, 151--Dimetholagiines 151—Dis- 
tinction between three types of amines, 152. 


CHAPTER XIX.—D1azo Compounps. . . Pele iS ee 
Phenol, 153—Iodobenzene, 154-7 Tolan 154—Diazo- 
aminobenzene, 156—Aminoazobenzene, 156—Phenylhydrazine, 
157. 


CHAPTER XX.—Aromatic ALCOHOLS, PHENOLS, AND ErHERS. . . 160 
Benzyl: alcohol, 160—Diphenylearbinol, 161—Diphenylethylear- 
binol, 161—Phenol, 162—General reactions of phenols, 163— 
Anisol, 164. 


CONTENTS xi 


PacE 
CHAPTER XXI.—Aromatic Acips. . . . . 165 
Benzoic acid, 165—Benzanilide, iipeeren irate: ene Fanilc 
acid, fee inamnic acid, 167—Terephthalic apie 168—Di- 
rath! terephthalate, 168. 


CHAPTER XXII.—Aromatic ALDEHYDES, KETONES, AND QuUINONES 170 
Benzaldehyde, 170—Benzophenone, 171—Benzophenoneoxime, 
172—Quinone, 172—Anthraquinone, 174. 


CHAPTER XXIII.—Aromatic Compounps CoNnTAINING Two oR 
DUEMMIN A EBECCRGOUPS (re 4 ee ta ee ge Oe ee LTS 
o-Nitrophenol, 175—Eugenol, 176—Sulphanilic acid, 177—m- 
Nitraniline, 177—p-Nitraniline, 178—Salicylic acid, 179—Tannic 
acid, 180. 


CHAPTER XXIV.—Dyss anp DyEInc . . . . 183 
Methyl orange, 183—Malachite green, ipseulioresnern. 185— 
Eosin, 186—Dyeing with congo, 186—Mordants, 187—Primuline, 
187. 


CHAPTER XXV.—HETEROcYcLIC COMPOUNDS. . . . 189 
Thiophene, 189—Furfuraldehyde, 189—Pyridine, LSU Cuioline. 
190—Alkaloids, 191. 


CHAPTER XXVI.—PROTEINS . . . . 192 
Detection of nitrogen, sulphur, ae pisephorust yee tan 
tion reactions, 193—Color reactions, 194—Gelatin and wool, 195 
—Salting out, 196—Hydrolysis of proteins, 196—Proteoses and 
peptones, 197—Proteins of wheat, 197—Edestin, 198—Casein, 
199—Textile fibers, 199. 


CHAPTER XXVII.—Tue IDENTIFICATION OF ORGANIC CompouNDsS. 202 
are I re ek ce ee ee wy we valet « oe 6208 


Sie Sere 4S pn Ree Ue eee ote 





EXPERIMENTAL ORGANIC 
CHEMISTRY 


CHAPTER I 
LABORATORY METHODS 


1. General Directions to the Student.—Before beginning an 
experiment read through to the end the directions which are to 
be followed. Many mistakes which involve additional work can 
be prevented by understanding beforehand just what is to be 
done. The import of the experiment should be clear, and the 
chemical reactions involved at each step should be understood 
before the work is started. 

References are given in each experiment to the section in the 
author’s text-book ‘‘The Principles of Organic Chemistry”’ in 
which the chemical reactions involved are discussed. These 
references are given in bold-face type thus, (Section 359). 
References to paragraphs in this book are indicated thus, $64, 
page 42. 

Keep a clear and concise record of the laboratory work. The 
notes should be written as soon as the experiment has been per- 
formed, and care should be taken to have the original record, 
made during the course of the experiment, of such a character 
that it serves as the permanent record of the work. Notes 
should not be taken on loose pieces of paper and afterward 
written out in the notebook; they should be written carefully 
in good English, and should state briefly what was done and what 
was observed. It is necessary for the student to recognize what 
the experiment is to teach—why he was asked to do it. If the 
work consists in the preparation of some compound the details 
for which are given in the laboratory guide, it is not advisable 
to take time to copy these details in the notebook. References 
to the pages in the book where the preparation is described should 

1 


2 EXPERIMENTAL ORGANIC CHEMISTRY 


be given, and a statement made of the amounts of the substances 
used. If any unexpected difficulties arose, or if any improve- 
ment in the way of carrying out the preparation was used, these 
facts should be noted. Write equations for all reactions taking 
place in the experiment, and record the yield of the compound 
obtained. The substance should be put in a clean, dry, glass- 
stoppered bottle of appropriate size, and be labeled. The 
student’s name, the name, weight, and the boiling-point or 
melting-point ef the substance should be recorded on the label. 
The boiling-point or melting-point should be that observed by the 
student for the sample itself, and not the points recorded in the 
book. 

The student should use reasonable care in his manipulations. 
He should endeavor to get as large a yield as possible of the 
product sought, but should use judgment as to whether it is 
advisable to spend a large amount of time to increase by a small 
amount the yield of the product. The processes should not be 
carried out in the manner used with a quantitative analysis—a 
few drops may be lost here and there if they form but a very 
small portion of the total amount formed, and their recovery 
entails the expenditure of much extra time. It is not meant 
by this that the student be careless; he should develop judgment 
as to the relative value of a slightly higher yield of product and 
the time required to obtain it. 

2. Calculation of Yield.—The student should calculate in each 
preparation the percentage yield obtained. From the chemical 
equation for the reaction can be calculated the so-called theoretical 
yield. The percentage of this obtained is called the percentage 
yield. The latter is never equal to 100 per cent for many reasons. 
It is often advisable to use an excess over the theoretical amount 
of one of the substances used in the preparation. ‘The student 
should, before calculating the percentage yield obtained, deter- 
mine whether an excess of one reagent has beenemployed.. When 
one substance used in a preparation is much more expensive than 
the rest, 1t is customary to take the substances in such amounts 
that the largest yield possible calculated from the more expensive 
substance is obtained. For example, preparations involving the 
use of iodine are so carried out that the largest amount of the 
halogen possible is obtained in the substance prepared. In this 


LABORATORY METHODS 5) 


case the test of the skill with which the preparation is carried out 
is determined by this fact; the percentage yield should be cal- 
culated, accordingly, from the weight of iodine used. 

3. Integrity in Laboratory Work.—The student should record 
in his notebook his own observations only, and the results he 
has obtained himself, unless there is a definite statement to the 
contrary. If a student has carried out an experiment along 
with another student a statement to this effect should be put 
into the notes. 

4, Cautions in Regard to Laboratory Work.—A student uses 
in laboratory work in organic chemistry inflammable liquids and 
substances like sodium and phosphorus which have to be handled 
with great care. Asa result fires may happen. The laboratory 
should be provided with buckets of sand and a fire-extinguisher. 
A heavy woolen blanket should be near at hand to be used in 
case the clothing catches fire. 

Inflammable liquids such as ether, alcohol, and benzene should 
not be poured into the jars provided for acids. 

Only cold solutions should be extracted with ether, and the 
process should be carried out at least twelve feet from a flame. 

When carrying out a reaction in a test-tube, care should be 
taken to hold the tube in such a position that if the contents are 
violently thrown out, they will not come in contact with the ex- 
perimenter or any one in the neighborhood. If the odor of a 
substance in the tube is to be noted, do not look down into the 
tube. Ii this is done and a violent reaction takes place suddenly, 
the material in the tube may be thrown into the eye. 


CRYSTALLIZATION 


5. When an organic compound has been prepared it must 
be purified from the by-products which are formed at the same 
time. In the case of solid substances crystallization is ordinarily 
used for this purpose, although with certain compounds purifica- 
tion can be more readily effected by sublimation or distillation, 
processes which are described below. 

Choice of Solvent.—The separation of two substances by 
means of crystallization is based on the fact that they are present 
in the mixture to be separated into its constituents in different 


4 EXPERIMENTAL ORGANIC CHEMISTRY 


amounts, or on the fact that the two substances possess different 
solubilities in the liquid used as a solvent. When it is desired 
to purify a substance by crystallization a solvent should be 
selected, if possible, in which the impurity is readily soluble, 
and in which the substance sought is more or less difficultly 
soluble. Purification is effected most easily when the sub- 
stance to be purified is appreciably soluble in the hot solvent, 
and much less soluble in it when cold. If the two conditions 
stated above can be combined—and this is possible in many 
cases—purification is readily accomplished. 

The solvents most commonly used in crystallization are water, 
alcohol, ether, benzene, petroleum ether, ligroin, carbon bi- 
sulphide, chloroform, acetone, and glacial acetic acid. In certain 
cases hydrochloric acid, carbon tetrachloride, ethyl acetate, 
toluene, and nitrobenzene have been found of particular value as 
solvents. 

In order to crystallize a compound the solubility of which is 
not known, preliminary tests should be made with the solvents 
enumerated above; about 0.1 gram or less of the substance should 
be used in each test. The solid is placed in a small test-tube, 
and the solvent is added a drop at a time and the tube is shaken. 
After the addition of about 1 cc. of the liquid, if the substance 
has not dissolved, the tube should be heated until the liquid 
boils. If the substance does not dissolve, more liquid should be 
added in small quantities until solution occurs. If a very large 
amount of the liquid is required for solution, or the substance 
proves insoluble, another solvent must be used. When solution 
takes place the tube is cooled by running water. If the substance 
separates, it is redissolved by heating, and the contents set aside 
to cool slowly, when crystals will probably form. 

If the substance does not separate to a considerable degree 
when the hot solution is cooled, similar tests should be made 
with other liquids. If none of the solvents can be used in this 
way, either the substance must be obtained by spontaneous 
evaporation, or a mixture of liquids must be used—a method 
described below. 

If the compound is to be crystallized by spontaneous evapora- 
tion, cold saturated solutions, prepared by dissolving about 0.1 


LABORATORY METHODS 5) 


gram or less of the substance in a number of solvents, are poured 
onto watch-glasses and left to evaporate slowly. 

6. Some substances form solutions from which the first crystals 
separate with difficulty. In such cases the solution is “‘seeded”’ 
by adding a trace of the solid substance; a piece the size of the 
head of a small pin is sufficient. Crystallization of such sub- 
stances can often be brought about by scratching with a glass 
rod the side of the vessel containing the solution; the rough sur- 
face so formed assists materially in the formation of the first 
crystal, after which crystallization proceeds readily. 

The liquid finally selected for the solvent should be one which 
yields well-formed crystals, and does not evaporate too slowly. 

7. Use of Freezing Mixtures in Crystallization.—It often 
happens that substances which do not separate from their hot 
solutions when the latter are cooled with water, crystallize out 
well when the solutions are allowed to stand for some time in a 
freezing mixture. For this purpose, a mixture consisting of 
equal weights of sodium chloride and jinely divided ice or snow, 
-is commonly used; with snow a temperature of —17° is obtained. 
A mixture of equal weights of crystallized calcium chloride and 
snow gives the temperature —48°. A convenient freezing mix- 
ture is made by covering finely divided ice with commercial 
concentrated hydrochloric acid. 

8. Preparation of Crystals.—When a satisfactory solvent has 
been selected, the material to be crystallized is placed in a beaker 
and covered with the liquid. The mixture is heated to boiling 
over a free flame or on a steam-bath if the solvent used is in- 
flammable. It is essential to avoid the presence of a free flame 
when alcohol, benzene, ether, or petroleum ether are used as 
solvents. The beaker is covered with a watch-glass, and the 
solvent is added in small portions at a time until the substance 
to be crystallized has passed into solution. It may happen that 
a small amount of a difficultly soluble impurity is present; in 
this case it is not advisable to add enough solvent to dissolve 
the impurity. 

When the substance to be crystallized has been dissolved, the 
solution is filtered while hot through a fluted filter-paper into a 
beaker. Crystallizing dishes should not be used. If the sub- 
stance crystallizes out during the filtration, either a hot-water 


6 EXPERIMENTAL ORGANIC CHEMISTRY 


funnel can be used, or enough of the solvent can be added to 
prevent crystallization. * In the latter case, and whenever an 
excess of solvent has been used, it is advisable to concentrate 
the solution to crystallization after filtration. 

9. The solution is evaporated to crystallization by boiling it 
gently. Tests are made from time to time to determine whether 
crystals will form when the solution cools. This can be readily 
done by placing a glass rod in the hot solution and then with- 
drawing it; if crystals appear when the drop of the liquid which 
adheres to the rod cools, the solution should be set aside and 
covered with a watch-glass or filter-paper. If crystals are not 
formed, the evaporation should be carried further. 

A hot-water funnel is at 
times very useful if crystals 
form during the filtration. It 
consists of a funnel surrounded 
by a metal jacket in which is 
placed water that can be 
heated to its boiling-point by 
means of a Bunsen burner. 
When inflammable liquids are 
used as solvents, the water 
ot should be heated and the bur- 
ner extinguished before filtra- 
tion. Disregard of this pre- 
caution has frequently led to 

Mgt fires. | | 

10. It is advisable to cut off 
the stems of the funnels to be used in the preparation of or- 
ganic compounds. This eliminates the clogging of the funnel as 
the result of crystallization of solids in the stem. It also makes 
it unnecessary, in most cases, to use filter-stands as the funnel 
can be supported by the beaker which is to hold the filtrate; 
if the beaker is too large for this, the funnel can be supported 
on a clay triangle placed on the beaker. The arrangement 
represented in Fig. 1 is especially convenient for filtering solu- 
tions which deposit crystals on cooling slightly. During filtra- 
tion the beaker is heated on the steam-bath or over a flame; 
the vapor which rises heats the funnel. The latter should be 















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i 


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(ee 


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| 





“ 


a 


LABORATORY METHODS 7 


covered with a watch-glass to prevent loss of heat during filtra- 
tion, from the liquid that it contains. 

11. The Use of a Mixture of two Liquids as the Solvent in 
Crystallization.—It is advisable to use as a solvent in purifying 
a substance a liquid in which the substance is readily soluble 
when heated and difficultly soluble in the cold. If such a solvent 
can not be found, a mixture of two miscible liquids is often used— 
one in which the substance is readily soluble, and one in which 
it is insoluble or difficultly soluble. In crystallizing a substance 
in this way it is first treated with the hot liquids which dissolve 
it; to the solution is then added the second liquid, also hot, 
until the mixture begins to cloud. A little of the solvent is 
added to clear up the solution, which is then covered to prevent 
too rapid evaporation, and the mixture is set aside to crystallize. 
Pairs of liquids which are valuable for crystallization in this 
way are alcohol and water, alcohol and benzene, petroleum 
ether and benzene, and alcohol and carbon disulphide. 

12. Separation of Crystals.—The separation of crystals from 
the mother-liquor is effected by filtration under diminished 
pressure. A funnel is attached to a filter-bottle by means of a 
rubber stopper. A perforated plate about 4 cm. in diameter is 
placed in the funnel and covered with a circular piece of filter- 
paper the diameter of which is about 6 mm. greater than that of 
the plate. This paper is moistened with the solvent. The 
bottle is connected with the suction-pump, and air is drawn 
through the apparatus. The paper is fitted into place so that 
it covers the joint between the filter-plate and funnel. If a 
crust has formed around the beaker at the surface of the liquid 
from which the crystals to be separated have formed, it should 
be carefully removed, as it will probably contain some of the 
impurities present. The remaining solution and crystals are 
then poured into the funnel, and the suction applied. When all 
the liquid has been drawn off the solid should be pressed down 
tightly with a spatula. The connection with the pump is broken, 
and the solid on the funnel is moistened with some of the pure 
solvent used for crystallization. The crystals are allowed to 
absorb the solvent and to stay in contact with it for about half 
a minute. The suction is then applied and the crystals drained 
as fully as possible from the liquid. The filter-bottle is again 


a 


8 EXPERIMENTAL ORGANIC CHEMISTRY 


disconnected from the pump, and the crystals covered again with 
the solvent, and washed as before. Crystals should never be 
washed by pouring the solvent over them while the filter-bottle 
is connected with the pump. If this is done a large amount of 
liquid is required to wash the crystals, and there is great loss due 
to the solution of the crystals in the solvent. 

When the crystals have been freed by suction as much as 
possible from the liquid used to wash them, they should be re- 
moved to a porous plate and allowed to dry spontaneously in the 
air. 

13. In the preparation of many compounds tarry substances 
are often obtained along with the compound desired. In this 
case the crystals first obtained from solution are often mixed 
with these substances. The tar may be removed by pressing 
the crystals on a porous plate and allowing them to stand un- 
disturbed for some time. The residue, from which the tar has 
been largely removed as the result.of absorption into the porous 
plate, is transferred to a clean part of the plate and is moistened 
with the solvent. The substance is left until the solution of the 
tarry product clinging to the crystals is absorbed. A second 
crystallization and treatment with the porous plate generally 
yields a pure compound. 

When the crystals are thoroughly dry a melting-point de- 
termination (§49, page 32) should be made; if this is not sharp 
the substance should be recrystallized. 

14. Decolorization of Solutions——If a substance contains 
tarry materials which impart to it a color it can be purified usually 
by boiling a solution of it for some time with bone-black, and 
filtering the hot solution. The efficiency of the process and the 
amount of bone-black required are markedly affected by the 
quality of the latter. As an approximation about 1 gram should 
be used for a solution of 250 cc. which is moderately colored. 


DISTILLATION 


15. Liquids are purified by distillation. The form of apparatus 
ordinarily used is represented in Fig. 2. In setting up the ap- 
paratus the details noted below should be considered. 

The distilling flask should be supported by a clamp placed 


LABORATORY METHODS 9 


above the side-arm, and the condenser by a clamp placed at its 
middle point. The side-arm of the distilling flask should extend 
for about one-half its length into the inner tube of the condenser. 

16. Preparation of Corks.—Before being used corks should be 
softened. This can be done by means of a press, which is made 
for this purpose, or the cork can be rolled on the desk while it is 
being pressed firmly by means of a block of wood. It is, in most 
cases, not advisable to use rubber stoppers as they may be 
attacked by the vapor of the liquid during distillation. Sharp 
cork borers should be used to make the holes of such a size that 


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Nira. 2. 


the tubes to pass through fit snugly. In boring corks it is ad- 
visable first to push the borer with a rotary motion half way 
through the cork, taking care that the hole is bored through the 
center of the cork; the borer is then removed and a hole made 
from the center of the other end of the cork to meet that first 
made. By proceeding in this way the edges of the holes on the 
two sides of the cork will be clean cut, and thus make a tight 
joint with the tube to be passed through the hole; and the latter 
will run evenly through the axis of the cork. 

17. Position of the Thermometer.—The bulb of the thermom- 
eter should be so placed that it is about 1 inch below the side- 


10 EXPERIMENTAL ORGANIC CHEMISTRY 


arm of the distilling flask. If the liquid boils at such a point 
that the end of the thread of mercury is hidden by the cork 
during the boiling, the position of the thermometer can be shifted - 
downward, or the upper or lower end of the cork can be cut away. 
The bulb should never be placed above the side-arm, since it 
is essential that it be covered completely by the vapor during 
the distillation. 

18. Heating the Flask.—The best way of heating the distilling 
flask is determined by the boiling-point of the liquid to be dis- 
tilled. If the liquid has a low boiling-point, up to about 80° or 
90°, the flask should be placed in a water-bath in such a position 
that the level of the water is just below that of the liquid in the 
flask. Toward the end of the distillation the flask should be 
_raised in order to prevent superheating the vapor of the liquid. 
With very volatile liquids great care is necessary to pr event this 
superheating. 

Another method which is often used is to place the flask on 
an asbestos board in which a hole is bored having a diameter 
about one-half that of the flask. The smallest flame which will 
furnish heat enough to boil the liquid is used. This method can 
be used for distilling in general, whatever the boiling-point of 
the liquid. 

If a flask of 250 ce. capacity or greater is used, it is advisable 
to support it on.a wire gauze. This precaution is also advisable 
when the burner is put in place, and the distillation allowed to 
take place of itself. It is often better to hold the burner in the 
hand and keep the flame in motion during the distillation. In 
this way the process is more carefully watched and the rate of 
distilling can be controlled. 

The heating of the flask should be discontinued pelo all of the 
liquid has distilled; it is customary to leave a residue of 2 to 5 cc. 
in the flask. 

19. Rate of Distillation.—The distilling flask should be heated 
in such a way that the distillate falls in drops from the end of the 
condenser at the rate of about one drop per second. Care 
should be taken to avoid the rapid distillation of very volatile, 
inflammable liquids, such as ether, alcohol, and carbon disulphide. 
If such liquids are distilled very rapidly, a part of the vapor is 
not condensed, and a fire may result when this vapor comes in 


LABORATORY METHODS 11 


contact with a near-by flame. In order to prevent accidents 
the method of collecting such liquids which is described in §34, 
page 23, should be used. 

20. Distillation of High-boiling Liquids.—When a liquid boils 
above 150° an ‘‘air-condenser’’ should be used instead of the 
kind shown in Fig. 2, which is supplied with a water-jacket. 
If one of the latter type is used, the inner tube, cooled by running 
water, is apt to crack when the vapor of the high-boiling liquid 
comes in contact with it. The inner tube without a jacket is 
used as an air-condenser. When a substance which boils at a 
high temperature (above 300°) and solidifies readily is distilled, 
it is customary to use no condenser, but to collect the distillate 








ple ES 6) 


Sur 





Fig. 3. : Fig. 4. Hig. 5. 


directly at the end of the side-arm of the distilling flask. If, 
in this case, or when an air-condenser is used, the distillate solidi- 
fies before it reaches the receiver, the tube should be gently 
heated by passing the flame of a burner slowly along its length. 
It is necessary to prevent the filling of the side-arm of the flask 
with solid; if this occurs and boiling is continued, the vapor 
produced soon reaches a sufficient pressure to cause an explosion. 
-~ When this method is unsatisfactory on account of the high 
melting-point of the substance, it is advisable to distil from a 
retort. On account of the large diameter of the neck of the re- 
tort, a considerable quantity of the solid can be collected in it. 
Before the solid fills the neck at any point, the distillation is 


12 EXPERIMENTAL ORGANIC CHEMISTRY 


stopped, the neck of the retort is heated, and the liquid collected 
in a beaker; the distillation is then continued. 

21. Fractional Distillation. When it is necessary to separate 
two or more liquids by distillation, special forms of distilling 
flasks should be used. These are so constructed that they de- 
crease materially the time required to effect a separation. This 
is accomplished by subjecting the vapor to gradual cooling before 
it is finally condensed. In this way the less volatile constituents 
of the vapor are condensed and returned to the flask, while the 





Fia. 8. Fig. 9. 


more volatile parts pass on through the condenser. The types 
of flasks used are illustrated by figures 3, 4, and 5. ( 

The arrangement represented in Fig. 5 is very efficient, 
especially when a small amount of a liquid is to be fractionated. 
After the liquid has been placed in the flask, a number of glass 
beads tied together with a cotton thread are supported by the 
thread, and the neck of the flask is filled to the place indicated - 
in the diagram with glass beads. 

22. The more complicated arrangements are supplied as 
tubes which are fitted by a cork to a round-bottomed flask. 
Figures 6, 7, 8, and 9 illustrate the forms commonly used. 


LABORATORY METHODS 13 


The most efficient form is that of Hempel, Fig. 9, which con- 
sists of a tube filled with glass beads. The least efficient form 
is that of Wurtz, Fig. 6. The efficiency of the Lebel-Henninger 
tube, Fig. 7, and of the Glinsky tube, Fig. 8, lies between the 
two extremes stated. 

23. When a mixture of two liquids which boil at different 
temperatures is distilled, the temperature of the vapor during 
the distillation rises, in most cases, from the boiling-point of 
one of the liquids to that of the other. The distillate which is 
collected first contains a large proportion of the lower boiling 
liquid, while that collected toward the end of the operation is 
rich in the higher boiling liquid. In order to separate the two, 
the mixture is subjected to what is called fractional distillation. 

The process is carried out in the following way: The mix- 
ture is distilled slowly, and the receiver in which the distillate 
is collected is changed from time to time, as the boiling-point 
of the liquid rises. In this way the mixture is separated into 
what are called fractions. The number of fractions collected, and 
the limits of the boiling-point of the various fractions, are deter- 
mined by the difficulty of separating the mixture and the purity | 
of the products desired. The lowest boiling fraction is next 
placed in a clean flask and distilled. When the temperature 
reaches that of the upper limit of the fraction, the heating is 
stopped, and the second fraction added to the flask. Distilla- 
tion is then continued until the upper limit of this fraction is 
reached, the distillate being collected in the appropriate receiver. 
The process is continued in this way until all the fractions have 
been distilled a second time. It will be found as a result of this 
fractionation that the distribution of the liquid in the several 
fractions is different from that obtained the first time. The 
fractions which boil at temperatures near those of the boiling- 
points of the constituents of the mixture increase in volume. By 
repeating the process a sufficient number of times, practically 


all of the liquid can be separated into its constituents. 


In the following table are given the results of the fractional 
distillation of a mixture of 50 cc. of methyl alcohol and 50 cc. 
of water. The volumes of the fractions obtained after each of 
six fractionations are recorded. 


14 EXPERIMENTAL ORGANIC CHEMISTRY 




















66°-68° 68°-78° | 78°-88° 88°-93* | D8" 10073 
I 0.0 Leo 47.0 17.0 31.0 
II 0.0 33.5 14.0 toa: 38.5 
Ill 1.5 38.5 6.5 5.5 40.5 
IV 15.0 24.5 5.0 3.0 43.5 
V 25.0 16.0 2.5 1.0 44.5 
VI 32.0 7.5 1.0 0.0 45.5 











When the liquids form a constant-boiling mixture, they can 
not be separated in pure condition by fractional distillation. The 
boiling-point of a mixture of ethyl alcohol and water, which 
contains 96 per cent by weight of the former, is lower than that 
of pure alcohol. As a consequence, when a mixture of the two 
substances is subjected to repeated fractional distillation, the 
constant-boiling mixture is obtained. In order to prepare pure 
alcohol it is necessary to remove the water from the mixture by 
chemical means. Very few cases of this kind are met with in 
the purification of organic compounds. 


DISTILLATION UNDER DIMINISHED PRESSURE 


_ 


24. Many substances which decompose when distilled at 
atmospheric pressure, distil without decomposition when the 
pressure is reduced. This results from the fact that the tempera- 


ture at which a substance boils is markedly affected by the pres- — 


sure. For example, benzophenone boils at 306° at 760 mm. 


pressure, and at 170° at 15 mm. pressure. The effect of change — 
in pressure on the boiling-point increases rapidly as the pressure — 


decreases. Stearic acid, for example, boils at 291° at 100 mm., 
at 232° at 15 mm., and at 155° under the best vacuum obtainable 
with a mercury pump. A difference of 85 mm. in pressure from 


100 mm. to 15 mm. causes a change in boiling-point of 59°, — 


whereas a difference of 15 mm. from 15 mm. to 0 mm. lowers the . 
boiling-point 77°. 

Many substances which distil with partial decomposition at 
atmospheric pressure can be distilled unchanged at the pressure 
which can be obtained with a good water-pump. A convenient 





| 
: 


LABORATORY METHODS 15 


arrangement of the apparatus required for distillation under 
diminished pressure is represented by Fig. 10. 

The flask to contain the substance to be distilled is fitted with 
a thermometer and a tube (a) which is drawn out to a fine open- 
ing at one end; to the other end of the tube is attached a piece 
of rubber tubing carrying a screw-clamp (b). This tube is pro- 
vided to prevent violent bumping during the distillation. By 
regulating the screw-clamp after the apparatus has been attached 


ery 








SSS 


oS 
SSS 





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N 








H 
SS 


VSS 
icacs SEE 
: 
Hill 


to the vacuum-pump, a rapid stream of air-bubbles can be drawn 
_ through the liquid. As the latter is heated the vapor formed 
passes into the bubbles, and superheating and the consequent 
“bumping” are largely avoided. The position of the tube isso 
adjusted that the fine opening almost touches the bottom of the 
flask. 
25. Other modifications of the form of the tube to admit air 
“into the flask are often used. If the neck of the flask is small 
and it is impossible to insert into it both the thermometer and a 
glass tube of the ordinary diameter, the part of the tube which is 
to pass through the cork is drawn out to a capillary, and is in- 


16 EXPERIMENTAL ORGANIC CHEMISTRY 


serted through a small hole made with a stout needle or the end 
of a file. One end of the tube is left with such a diameter that 
the rubber tubing and screw-clamp can be attached to it. 

26. A second modification is often used on account 
of its convenience. It is illustrated in Fig. 11. A 
straight glass tube is selected of such a diameter that 
the thermometer passes into it easily. The tube is 
drawn out at one end to a small opening; it is then 
cut off at the other end at such a point that when 
the thermometer is placed in it and it is put into the 
flask, the bulb of the thermometer is in the correct 
position with regard to the side-arm of the flask. A 
piece of rubber tubing provided with a screw-clamp 
is attached to the upper end of the tube. 

When liquids which boil at a very high tempera- 
ture are distilled, it is customary not to use an air- 
condenser, but to connect the receiver directly with 
the side-arm of the flask which contains the liquid to 
be distilled. 

In assembling the distilling apparatus, a rubber 
stopper may be used to attach the receiver to the 
condenser, provided care is taken to prevent the hot 
liquid from coming in contact with the rubber. Great 
care should be exercised in selecting the corks to be 
used; these should be as free as possible from holes. 
After the apparatus has been set up, small leaks can 
often be closed by painting the corks with collodion. 

A convenient arrangement of the manometer and 
the connections between the pump and the receiver are 
represented in Fig. 10. A number of forms of ma- 
nometers are used to register the pressure inside the 
apparatus. A simple form which can be readily made 
from a supply of mercury, a meter-stick, and a piece 
Fic. 11. of glass tubing is illustrated in the figure. In order 

to determine the pressure in the apparatus the read- 
ings on the scale opposite the levels of the mercury in the ma- 
nometer are subtracted, and this difference is subtracted from 
the height of the barometer. 

It is necessary to insert an empty bottle between the pump and 
















LABORATORY METHODS 17 


the receiver. When the apparatus has been evacuated, water 
may run back from the pump into the receiver as a result of a 
slight change in the pressure of the water caused by the opening 
of a cock in the neighborhood. The inserted bottle serves as a 
trap to catch this water. At c is a stop-cock through which air 
can be let into the apparatus. This is of value at the end of a 
distillation, or in case the boiling liquid begins to froth or bump 
violently. In the latter case letting in a little air prevents the 
ejection of a part of the contents of the flask into the receiver. 

27. Method of Distillation.—Before introducing the liquid to 
be distilled, the whole apparatus should be tested. The screw- 
clamp 6b should be closed, and the receiver connected by a heavy- 
walled tube to the pump. In no part of the apparatus should 
rubber tubing be used which collapses under diminished pressure. 
If no heavy tubing is available the connections can be made with 
glass tubing joined by ordinary rubber tubing, the ends of the 
glass tubes being brought together so that the connecting rubber 
tubes can not collapse. When the apparatus has been connected 
with the pump the pressure should be reduced to about 20 mm. 
If this can not be done, either the pump is a poor one, or the 
apparatus has not been well put together. The cause can be 
determined as follows: First, test the pump by connecting it 
directly with the manometer, making sure that there is not a 
leak in the connecting tubes. Second, disconnect the tube at 
d, and close it with a pinch-cock or glass rod. If the reduction 
in pressure is sufficient it will show that all the connections from 
the pump up to this point are tight. Next, disconnect the flask 
from the condenser and connect it by means of the side-arm to 
the pump and manometer. This will determine whether the 
cork provided with the thermometer and the tube to admit air 
is tight. It is probable that the leak will be found at this point. 
If everything is tight, connect the flask with the condenser, and 
the lower end of the latter with the pump. This will test the 
tightness of the joint between the flask and condenser. The 
apparatus is next completely adjusted, and tested again, when, 
if no leak has been discovered up to this point and the pressure 
can not be sufficiently reduced, it is evident that the connection 
between that condenser and receiver is at fault. 

When the apparatus has been found to be tight, the product 

z | 


18 EXPERIMENTAL ORGANIC CHEMISTRY 


to be distilled is introduced into the flask, which should be filled 
to not more than one-half its capacity. The suction is applied 
and the screw-clamp b opened very slowly sothat a stream of air- 
bubbles passes through the liquid. The flask is heated by a 
bath containing oil or, preferably, a low-melting alloy such as 
Rose’s or Wood’s metal. It is often better to heat the flask by 
means of a free flame as the amount of heat applied can be 
quickly regulated. When a free flame is used it should be kept 
in constant motion, and the surface of the liquid where it comes 
in contact withthe flaskshould be heated ratherthan the bottom 
of the flask. This can be done by moving the flame around 
the flask and letting it come in contact with the latter at the 
side and not the bottom. 

If frothing suddenly begins and there is a chance of the con- 
tents of the flask rushing over into the receiver, such a result 
can be prevented by opening the cock c which admits air to the 
apparatus. 

Special forms of apparatus have been devised to fractionate a 
liquid by distillation under diminished pressure. It is often 
simpler to use the apparatus described above, and change the 
receiver when the limits of the fractions have been reached. 


DISTILLATION WITH STEAM 


28. Substances which are practically immiscible with water 
and have an appreciable vapor pressure at 100°, can be readily 
separated from those which have a very small vapor pressure 
at this temperature by passing steam through the mixture. 
The process which is of special value in separating organic com- 
pounds from tarry materials found in their preparation, is carried 
out in an apparatus arranged as represented in Fig. 12. 

The flask a is connected with a supply of steam; this can be con- 
veniently generated in a kerosene can, which is supplied with a 
long glass tube reaching to the bottom of the can, to act as a 
safety-valve. Into the flask is put the substance to be distilled. 
The flask should be set up at an angle as indicated in the dia- 
gram. By placing the flask in this position any of the liquid 
which is violently thrown up against the flask as the result of 
the inrush of steam, will not be forced through the condenser 


LABORATORY METHODS 19 


into the receiver. The tube through which the steam is led 
should be so bent, that its end almost touches the lowest point of 
the flask in its inclined position. By this means the steam is 
forced through the heavy liquid to be distilled, which is conse- 
quently kept in motion. If the liquid is not stirred up by the 
incoming steam distillation takes place very slowly. 





Figs lz. 


29. The vapor issuing from the flask consists of a mixture of 
steam and the volatile substance to be distilled. When this is 
condensed, two layers are formed. The theory of the process is 
briefly as follows: When a mixture of two immiscible liquids 
is heated, each substance vaporizes independently of the other. 
When the sum of the vapor pressures of the two liquids is equal 
to the pressure of the atmosphere, the mixture distils. The 
relation between the weight of the two substances obtained is 
determined by their molecular weights and their vapor pressures 
at the temperature of distillation. The case of nitrobenzene 
and water is an example. When steam is passed into nitro- 
benzene the mixture boils at 99°, when the atmospheric pressure 
is 760 mm. At this temperature the pressure of water vapor is 
733 mm., and of nitrobenzene 27 mm.; consequently the relation 
between the weight of water and that of nitrobenzene is as 
18 X 733 is to 123 X 27, or approximately 4to1. Although the 


20 EXPERIMENTAL ORGANIC CHEMISTRY 


vapor pressure of nitrobenzene is small at 99°, its large molecular 
weight compared with that of water leads to the result that about 
one-fifth of the product obtained by distillation with steam con- 
sists of nitrobenzene. When the vapor pressure of a compound is 
as low as 10 mm. at 100°, it can be advantageously distilled with 
steam. Orthonitrophenol can be conveniently separated from 
paranitrophenol on account of the fact that the former has an 
appreciable vapor pressure at 100°, and is consequently volatile 
with steam. 

30. When the vapor pressure of a substance increases rapidly 
near 100°, the rate at which it distils can be markedly increased 
by adding to the mixture of it and water a substance solublein 
water; the latter increases the boiling-point of the liquid. By 
saturating the water with calcium chloride a marked rise in the 
temperature at which distillation occurs can be effected, with the 
consequent increase in the vapor pressure of yas Bee compound 
undergoing distillation. 

When the vapor pressure of a substance is appreciable only at a 
temperature considerably above the boiling-point of water, it 
may often be separated from less volatile compounds by-distilla-_ 
tion with superheated steam. In this case the flask containing — 
the substance is heated in an oil-bath, and steam which has been 
passed through a hot coil of copper is conducted through it. 


EXTRACTION 


By extraction is meant the processof removing from a mixture, 
usually an aqueous solution, one or more substances by shaking 
with a liquid in which the substances to be removed are soluble. 
Aniline, for example, is somewhat soluble in water; when the solu- 
tion is shaken with ether a large part of the aniline is removed 
from the water and passes into solution in the ether. As aniline 
can be recovered much more readily from an ethereal solution 
than from an aqueous solution, extraction of such solutions is 
made use of in the preparation of the compound. The liquid 
used for extracting must.be immiscible with the solution to be 
extracted. 

31. Method of Extraction.—In extracting a solution it is 
shaken in a separatory funnel with a liquid in which the substance 


e 


4 


LABORATORY METHODS 21 


to be extracted is readily soluble. The substances commonly 
used for this purpose are ether, chloroform, benzene, petroleum 
ether or ligroin, and carbon disulphide. Ether is generally 
used as it is an excellent solvent for many organic compounds, 
and, on account of its low boiling-point, it can be readily removed. 
The disadvantages connected with the use of ether are its great 
inflammability and the fact that it is somewhat soluble in water 
and dissolves appreciable quantities of water. Water dissolves 
approximately 10 per cent of its volume of ether. When large 
volumes of aqueous solutions are extracted there is a loss of 
ether, which is an expensive substance. This loss is decreased 
by saturating the solution to be extracted with sodium chloride. 
On account of the fact that ether dissolves about 2 per cent of 
its volume of water, ethereal extracts have to be dried, in most 
cases, before the ether is removed by evaporation. 

32. The relation between the volume of an aqueous solution 
to be extracted and the volume of the solvent used for extrac- 
tion, is determined by the relative solubilities of the substances 
to be extracted.in water and the solvent used. If an aqueous 
solution of a substance is extracted with ether, the amounts of 
-the substances found in the two liquids will be proportional to 
the solubilities in the two solvents and to the amounts of the 
_ latter. - If the substance is equally soluble in water and in ether, 
and the volumes of the two liquids are the same, after extraction 
one-half of the substance will be found in the ether. If the 
‘substance is twice as soluble in ether as in water, the relation 
of the amount present in the ether will be to that present in the 
water as two is to one, that is, two-thirds will be present in the 
ether and only one-third in the water. By shaking the aqueous 
solution with a second portion of ether, two-thirds of the sub- 
stance present, that is two-thirds of one-third, or two-ninths, of 
the original amount will be removed and one-ninth will remain 
dissolved in the water. After three extractions but one twenty- 
seventh of the substance will remain dissolved in the water. 

In the above example a certain volume of a solution was ex- 
tracted three times, using each time a volume of ether equal to 
that of the aqueous solution. The result would have been differ- 
ent if the solution had been extracted with the three volumes of 
ether in one operation. In this case the substances would have 


22 EXPERIMENTAL ORGANIC CHEMISTRY 


been divided between the ether and the water in the ratio of 
3 X 2:1; that is, one-seventh would have remained dissolved 
in the water. As the result of extracting the solution with the 
same volume of ether in three operations using one-third of the 
solution each time, but one twenty-seventh remains dissolved 
in the water. It is evident, therefore, that the most efficient 
way to extract a substance is to shake the solution a number of 
times with small amounts of the extracting agent. 

33. The relation between the volumes of the extracting liquid 
and of the solution, and the number of times the solution should 
be extracted, vary widely with the relative solubility of the sub- 
stance to be extracted. In general, in the case of a substance 
which is much more soluble in ether than in water, three extrac- 
tions will be sufficient if a volume of ether equal to about one- 
fourth of that of the aqueous solution is used. In order to de- 
termine whether the extraction has been carried far enough, a 
sample of the last ethereal extract should be evaporated on a 
watch-glass on a steam-bath. The amount of the residue will 
determine whether a fourth extraction is desirable. 

If a large volume of liquid is to be extracted, and a separatory 
funnel of appropriate size is not available, the liquid can be 
placed in a flask and shaken with ether; the major part of the 
latter can be decanted off, and the rest separated in a small — 
separatory funnel. | 

34. Separation of the Extracted Substance.—If the substance 
is a solid, and a small amount of the extracting liquid has been 
used, the solution can be evaporated to dryness and the residue 
crystallized. If itis desired to recover the ether or other solvent 
used in the extraction, the solution should be placed in a flask 
and the solvent distilled off on a water-bath as described below. 
When the substance to be obtained from the solution is a liquid 
which is to be finally distilled, it is necessary to dry the extract 
before the removal of the solvent. The drying agent must be 
selected according to the principles stated in §36, page 24. If 
ether has been used, the solution should not be set aside to dry 
in a thin-walled flask which has been stoppered; sufficient heat 
is at times generated as the result of the union of the water and 
the drying agent to break the flask. A bottle or distilling flask 
should be used. It is not advisable to place the extract in a 


LABORATORY METHODS 23 


beaker or other open vessel, as the solvent will be lost if the solu- 
tion stands for some time. 

When the solution is dry, the solvent can be removed by dis- 
tillation. If ether or any other very volatile and inflammable 
liquid is used, the flask containing the solvent should be heated 
on a water-bath, and should be provided with a long water- 
jacketed condenser and a special form of receiver. This is made 
by attaching to the condenser, by means of a tightly fitting 
stopper, an adapter, which, in turn, is attached in the same way 
to a filter-bottle. The side-arm of the latter is provided with a 
rubber tube of such length that it reaches nearly to the floor. 
By taking these precautions accidents caused by fires are pre- 
vented, as the only way in which ether vapor can escape from the 
apparatus is through the rubber tube; as ether vapor is very heavy 
and as any which escapes is delivered at the level of the floor, 
there is little chance of its being ignited by any flames on the 
laboratory desks. The receiver should be dry in order that the 
ether which distils over may be used in transferring the residue 
after the distillation to a flask of appropriate size for the final 
distillation. | 

The dry ethereal extract is decanted, or, better, filtered from 
the drying agent into the distilling flask, great care being taken 
to prevent any heavy aqueous layer from getting into the flask. 
Such a layer is frequently formed when potassium hydroxide is 
used as adrying agent; the compound extracts water from the ether 
and forms a saturated aqueous solution. The flask is next tightly 
corked, attached to the condenser and receiver, and the ether 
distilled off on a water-bath. When all the ether has evaporated 
the residue is poured into a flask of appropriate size for distilla- 
tion. As an appreciable amount of the substance adheres to 
the larger flask from which the etheral extract was distilled, it 
should be washed out twice with a few cubic centimeters of the 
ether which have been distilled off, and these washings added to 
the flask from. which the final distillation is to be made. In this 
distillation the flask should be heated slowly at first until the 
small amount of ether has been driven out. The final distilla- 
tion should be made as described in §15. 

35. Sublimation.—This process is of special value when it is 
desired to separate a solid which is volatile from substances 


24 EXPERIMENTAL ORGANIC CHEMISTRY 


which do not vaporize readily. It generally yields a very pure 
substance, but it often leads to loss. 

The process is most easily carried out between two watch- 
glasses which fit closely. The substance which has been carefully 
dried is placed in one of the glasses. This is covered with a piece 
of filter-paper, in which a few small holes have been cut to allow 
the passage of the vapor. The second glass, placed in an inverted 
position, is fastened to the first by means of aspecially constructed 
clamp. The apparatus is heated slowly on a sand-bath and the 
upper watch-glass is cooled by putting on it pieces of filter-paper 
which are kept moist with cold water. It is necessary to keep 
the upper watch-glass at a temperature lower than the melting- 
point of the substance to be sublimed. 

36. Drying Agents.—Many organic substances are prepared 
in water solution or in their preparation are washed with water 
to remove soluble impurities. In this case it is necessary to dry 
them, if they are liquids, before they are distilled. It is necessary 
to select as a drying agent a substance which does not react with 
the compound to be freed from water. The substance generally 
employed is anhydrous calcium chloride, which is commonly 
used in a granular form; for many purposes the chloride which 
has been fused in the form of sticks is preferable. Calcium 
chloride forms addition-products with hydroxyl compounds and 
should not be used as a drying agent for alcohols, phenols, ete. 

Alcohols are commonly dried with quicklime. Water is us- 
ually removed from basic substances by treating them with 
solid potassium hydroxide. Anhydrous copper sulphate is an 
excellent drying agent for most substances; another salt, anhy- 
drous sodium sulphate, is frequently used. It must be remem- 
bered in the latter case that hydrated sodium sulphate loses its 
water of crystallization at 33°; it is evident that the salt acts as 
a drying agent only below this temperature. 

The most powerful drying agents are sodium and phosphorus 
pentoxide. The use of the former is evidently limited to those 
substances which do not react with the metal. Sodium is used 
to remove the last traces of water only, the substances being 
previously dried with calcium chloride which removes most of 
the water. 

37. The drying agent should remain in contact with the 


LABORATORY METHODS | 25 


substances to be dried for from 2 to 3 hours, if the two are 
left in contact at room temperature. If convenient, the mixture 
should be set aside over night. 

Whether the drying agent should be removed from the sub- 
stance before it is distilled, is determined by the boiling-point 
of the substance and the stability of the compound formed be- 


AY 
6G: 
E 
e 
lS 
3 ie 
iS 
5 
: 





Scoarg : 
4 U 4 
H H 
H H 
H " 7 
H| “0 /; 

i} 

tH 0 
H 0 

is) V4, 

p 

i WY 

H i 
4 

if a 
, ice @" 

‘ \ 
¢ 0" 

0 


my LLM 





Fria. 13. 


tween the water and drying agent. It is advisable, however, 
except in the case of substances which boil below 80°, to remove 
the drying agent before distillation. 

The last traces of water may be removed from liquids which 
boil above 200° by drawing a current of air through them while 
they are gently heated. 

38. Use of the Reflux Condenser.—It is often necessary to 
heat together two or more substances for a number of hours. If 
all the substances boil above the room temperature an open vessel 
provided with a reflux condenser is used. The arrangement 
of the apparatus is shown in Figs. 13 and 14. 


26 EXPERIMENTAL ORGANIC CHEMISTRY 


If it is desired to distil the product formed directly from the 
flask, the arrangement represented in Fig. 14 may be used. 
In this case the side-arm of the distilling flask is covered with a 
cork into which a hole has been bored half through its length. 
The side-arm is so placed that the liquid which condenses in it 
returns to the flask. Heating with a reflux condenser is usually 
carried out in a round-bottomed flask as shown in Fig. 13. If 
the contents are apt to boil 
with bumping the flask is 
usually heated on a sand- 
bath; otherwise a free flame 
and a wire gauze are used. 
If the liquid boils above 150° 
an air-condenser is used in- 
» stead of a condenser provided 
“& with a water-jacket. 

When it is necessary to heat 
with a reflux condenser sub- 
stances which destroy cork 
and rubber, a simple device 
can be used which is repre- 
sented in Fig. 15. A test- 
tube is selected which fits 
loosely into a long-necked, 
round-bottomed flask. The 
tube is supplied with a rubber 
stopper and tubes as shown in 
the drawing. Water is 
passed through the tube, 
which is supported in the neck 
of the flask by means of a 
clamp. 

In many syntheses hydrogen chloride or bromide is given off. 
It is inadvisable to let these gases get into the room even when 
the apparatus is placed under a hood. The top of the condenser 
should be provided with a tube bent at two right angles. This 
tube should reach to about 1 inch of the surface of water contained 
in a flask supported by a ring-clamp to the stand to which the 
condenser is attached. If it is necessary to keep the contents 





LABORATORY METHODS 27 


of the flask dry during the reaction, a straight drying tube con- 
taining calcium chloride should be inserted between the con- 
denser and the flask containing the water. 

39. Prevention of Bumping.—When a substance 
boils irregularly and ‘“‘bumps,” even boiling can often 
be obtained by placing in the vessel a few pieces 
broken from a porous plate. The so-called capillary 
boiling tubes are also valuable. They can be made 
by drawing out pieces of glass tubing to stout capil- 
lary tubes; these are cut off at such a length that they 
will reach from the bottom of the flask to well into 
the neck. They are next put into the flame and 
melted at such a point that the tube fuses 
together at about 0.5 cm. from one end. 
When this end is placed under a_ liquid 
the small cavity is filled with air, and as 
the liquid boils bubbles of vapor are formed 
at the end of the tube and even boiling 
results. If the liquid cools below its boil- 
ing-point after it has been heated some 
time, the cavity at the end of the boiling 
tube becomes filled with liquid as the re- 
sult of the condensation of the vapor. In 
this case the tube must be withdrawn and 
the drop of liquid shaken from it, or a new 
tube must be inserted. E 

40. Dropping Funnels.—A dropping jy 46. 
funnel like that shown in Fig.16 is very 
useful. With a funnel of this type it is possible to 
observe at the point marked a the number of drops 
which pass through the funnel. If such a funnel is 
not available one can be made from an ordinary sepa- 
ratory funnel by attaching to its end 4 short calcium 
chloride drying tube as shown in Fig. 17, and con- 
necting the latter by means of a glass tube to the ap- 

Fig. 17, Paratus to be used. 

41. Manipulation of Sodium.—Sodium is used in 
the preparation of a large number of organic compounds. As 
the metal reacts rapidly with oxygen and with water-vapor, it 





28 EXPERIMENTAL ORGANIC CHEMISTRY 


should not be allowed to stay in contact with the air any longer 
than is necessary. When sodium is to be cut with a knife or 
pressed into a wire, the coating which covers the metal should 
be first carefully removed and rejected; and the sodium should 
be placed immediately under dry ether, if it is not to be used 
at once. In many preparations in which sodium is used a part 
of the metal is left unchanged at the end of the experiment. 
Great care must be exercised in getting rid of the residue. It 
should not be left in an unlabeled flask or bottle. Under no 
circumstances should the product be allowed to come into con- 
tact with water. Small quantities of alcohol should be added 
from time to time to the sodium, until enough of the liquid is 
present to dissolve the residue, or to make with it a thin paste. 
This mixture should then be poured slowly into water, in order 
to prevent an accident in case any sodium is enclosed within 
a mass of inert solid. When sodium is used in a preparation, 
great care should be taken to prevent water entering the vessel 
containing the metal, either as the result of using a poorly fit- 
ting cork or a defective condenser. 


Tue MANIPULATION OF SMALL QUANTITIES OF SUBSTANCES 


In the identification of organic compounds it is generally 
necessary to transform them into other compounds, the properties 
of which are determined as an aid in the identification. It 
often happens that but a few grams of a substance are available 
for the purpose. The successful handling of such small quantities: 
requires careful work, and the student should have opportunity 
to learn the special technique required. 

42. Crystallization.In the purification of small quantities 
of substances by crystallization a solvent should be selected in 
which the substance is more or less difficultly soluble, and care 
should be taken to avoid an excess of the solvent. It is best not 
to add enough of the solvent to completely dissolve the substance, 
even at the boiling temperature. The hot solution should be 
rapidly filtered. This can be done best under diminished pres- 
sure. A filter-bottle is selected of such a size that it will hold 
a 6-inch test-tube and permit a funnel being placed in the neck 
of the bottle in the usual way. The funnel is fitted with a per- 


LABORATORY METHODS 29 


forated plate and a circular piece of filter-paper which is cut 
with a diameter about 8 mm. greater than the plate. The paper 
is put in place and pressed down so that it covers the joint be- 
tween the plate and thefunnel. A little of the liquid is poured 
through the funnel and the suction applied. This serves to set 
the paper firmly in place. 

The liquid is poured out of the test-tube, which j is then replaced 
in the bottle. The funnel is put in place and the solution to be 
filtered is poured into it. Under the diminished pressure, the 
solution filters rapidly before the compound in solution can 
crystallize out. The method of filtration described in §10, 
page 6, is also to be recommended. 

43. A filter-bottle provided with a perforated plate and test- 
tube is used to separate crystals from the mother-liquor contain- 
ing them. While connected with the suction-pump the mixture 
of crystals and mother-liquor is poured slowly down a glass rod 
onto the filter-paper. If a very small amount of crystals is to 
be separated, care should be taken to collect them in a single spot 
and not to spread them outover theentire plate. In thisway the 
crystals can be collected in a small mound, a few millimeters in 
diameter, which can be readily removed from the paper when dry. 
The crystals should be washed as directed in §12, page 7. 

44. Distillation of Small Amounts of Liquids.—The liquid 
should be distilled from a 5 ce. distilling flask. If this is not 
available the neck of a broken distilling flask can be converted 
into a serviceable piece of apparatus for this purpose by sealing 
it at a point about 5 cm. from the side-tube. In distilling 
with small flasks an asbestos shield as described in §18, page 10, 
and avery small flame should always be used;a short thermome- 
ter reduces the error arising from stem-exposure. 

The boiling-point of 1 cc. of liquid can be determined in this 
way. In heating the substance, the flame should be applied, at 
first, in such a way that the vapor condenses in the flask just 
before it reaches the side-tube. In this way the thermometer is 
heated up to the temperature of the vapor before the latter is 
driven over. If the distillation is carried on rapidly the small ~ 
amount of liquid will have distilled over before the thermometer 
has been heated up to the temperature of the vapor. For a 
method of determining the boiling-point of very small quan- 


30 EXPERIMENTAL ORGANIC CHEMISTRY 


tities of a liquid see Smith and Menzies, J. Am. Chem. Soc., 
33, 897. 

45. If it is necessary to distil fractionally a small amount of 
liquid, a flask should be selected the side-arm of which is as far 
away from the bulb as possible (see Fig. 4, page 11). Such a 
flask can be furnished with an efficient fractionating column as 
follows: Glass beads which pass snugly into the neck of the flask 
are tied to the end of a cotton thread, or if necessary a fine 
platinum wire. After the liquid has been introduced, the beads 
are hung at the bottom of the neck of the flask, which is then 
filled with more beads, just enough room being left for the ther- 
mometer. A column of beads 
only a few centimeters high is 
remarkably efficient in bringing 
about the separation of liquids 
of different boiling-points 
through distillation (see Fig. 5, 
page 11). 

46. Extraction of Small 
Amounts of Substances.— When 
a small amount of substance is 
to be extracted the solution is 
», shaken with about an equal 
“® volume of ether or other solvent 
in a test-tube. To separate the 
two liquids the upper layer is 
drawn into a pipette. In order 
to be able to see clearly the posi- 
tion of the end of the pipette, 
a long rubber tube is connected with it so that the test-tube 
may be held at the level of the eye while the liquid is being 
drawn up. 

If a number of extractions are to be made a simple apparatus 
which can be made readily is of value. This consists of a test- 
tube with a side-arm placed at a point slightly above the middle 
of the tube. The tube is filled with the liquid to be extracted 
up to the side-arm, which is closed by the end of the forefinger. 
Ether is added, the tube closed with the thumb, and the mixture 
shaken. A vessel to hold the ether is placed under the side-arm; 





LABORATORY METHODS 31 


when the finger and thumb are removed the ether runs out, of 
the tube. 

47. Preparation of Liquids on the Small Scale.—It is often 
necessary to prepare small amounts of liquids, which are obtained 
as the result of heating together two or more substances, and 
subsequent distillation. An example is the preparation of ethyl 
iodide by heating alcohol and hydriodic acid. A simplified 
form of apparatus for such work is shown in Fig. 18. 

The test-tube a is supported by a clamp; the test-tube which 
serves as a condenser is surrounded by cold water contained in 
a beaker. It is important that the tube from a@ should extend 
nearly to the bottom of the condenser, in order that any vapor 
which passes over may come in contact with the walls of the 
tube, which are cooled by the water in the beaker. In using an 
apparatus like this, the distillation should be made very slowly. 


DETERMINATION OF PHYSICAL PROPERTIES 


48. Calibration of Thermometers.—The thermometers pro- 
vided for use in determining the physical properties of organic 
compounds are usually far from accurate. If very exact meas- 
urements are to be made, a high-grade thermometer should be 
calibrated according to the methods described in books dealing 
with physical measurements. For students’ work in organic 
chemistry, a cheap thermometer may be used provided it is cali- 
brated with reasonable care. A thermometer which is accurate 
to within 0.5° is satisfactory. 

Although most thermometers register correctly at 0° and 100°, 
it is well to make a calibration at these points. To determine the 
reading at 0°, a beaker of 100 cc. capacity is filled with finely 
chopped ice, and water is added until it. reaches to within about 
2 cm. of the surface of the ice. The thermometer is inserted into 
the ice and water until the zero point is just above the surface, so 
it can be seen. The reading on the thermometer is noted when 
_the mercury no longer falls. Care should be taken to have the 
eye at the height of the top of the mercury column to avoid 
parallax. 

To calibrate the thermometer at higher temperatures it must 
be heated in such a way that the entire mercury thread is exposed 


32 EXPERIMENTAL ORGANIC CHEMISTRY 


to the vapor of a boiling liquid. This can be conveniently done as 
follows: Attach to an 8-inch test-tube by means of a closely 
fitting cork (not a rubber stopper) a short air-condenser. Place 
in the tube about 10 cc. of water, and support the tube and 
condenser by means of a clamp over a wire gauze. Attach a 
cotton thread to the thermometer, and lower it through the 
condenser until the bulb is about 4 inches above the liquid. The 
thermometer is held in place by tying the upper end of the thread 
around a small piece of glass rod, which is then placed across 
the end of the condenser. The water is boiled, and when the 
entire thermometer is in the vapor, the position of the mercury 
is noted. 

The thermometer should be calibrated at higher temperatures 
by determining the boiling-points of other liquids in the apparatus 
described above. The latter should be thoroughly dried and a 
fresh cork used to avoid the presence of water. The substances 
which can be used conveniently are aniline, naphthalene, and 
benzophenone. The boiling-points of these substances at 760 
mm. pressure are, respectively, 183.7°, 218.1° and 306.1°. These 
are the temperatures recorded when the entire thread of mercury 
in the thermometer is exposed to the vapor of the boiling liquid. 
The barometric pressure should be noted and a correction made 
of 0.1° for each 2.7 mm. of pressure; if the observed pressure is 
less than 760 mm. the correction should be added, and if greater 
it should be subtracted. The substances used should be pure; 
the aniline must be redistilled, and the first part of the distillate 
rejected, in order to free it from the small amount of water that 
it usually contains. The thermometer should be marked with 
a number, and the corrections to be applied recorded in the note- 
book. 

49. Determination of Melting-points.—A form of apparatus 
which can be conveniently used to determine melting-points is 
represented by Fig. 19. It consists of a 100 cc. round-bottomed 
flask and a test-tube which fits loosely into the neck of the flask. 
A thermometer is supported in the test-tube by a cork in which a 
slit has been cut so that the graduations of the former are visible. 
The flask and test-tube are filled with pure concentrated sulphuric 
acid to the heights indicated in the drawing. If the sulphuric 
acid becomes brown as the result of the introduction of traces 


LABORATORY METHODS 33 


of organic matter, a tiny piece of a crystal of potassium nitrate 
will destroy the color. 

The substance, the melting-point of which is to be determined, 
is dried, usually in the air, and is powdered by rubbing it with 
a spatula on a clean porous tile. It is then placed in 
a small capillary tube which has an internal diameter 
of about. 1 mm. 

50. Tubes for the determination of melting-points are 
conveniently made as follows: A piece of glass tubing of 
5 mm. internal diameter is softened by rotating it ina 
flame; it is removed from the flame and after 2 seconds 
is slowly drawn out so that the tube is 
elongated about 10 cm., and the tube 
formed has at its narrowest point an ex- 
ternal diameter of about 1.45 mm. The 
tube is again heated and drawn out. The 
process is repeated until the tube is of 
such a length it can not be conveniently 
handled. The appearance of the tube so 
prepared is represented by Fig. 20. 

The distance from ato c should be about 
15 cm. The tube is cut at a, c, e, etc. 
These pieces are then cut in the middle at 
b, d, etc., and each piece sealed at these 
points by holding -in a flame. A number 
of tubes should be prepared at one time. 
In order to avoid getting dust into the 
tubes, they should be kept in a test-tube 
provided with a cork, or should be placed 
in a small beaker with the open ends down- 

ward. 
=== The substance to be melted is placed in 
a tube. This can be done readily by press- 
eee ing a little of the substance into the open end 

Fic. 19. Of the tube with the aid of a spatula, grasp- 

ing the tube by the closed end, and draw- 
ing a file lightly over it. The vibrations produced in this way 
cause the powder to fallin the tube. The process is repeated until 


a layer of the substance from 0.5 to 1 cm. thick has been formed. 
3 


Fre. 20. 





SS SUT TTC) 





a Ru 









hy 
ae 









34 EXPERIMENTAL ORGANIC CHEMISTRY 


The tube is attached to the thermometer by means of a rubber 
band which is made by cutting off a piece of tubing about 2 mm. 
in length from a rubber tube of such a diameter that it fits the 
thermometer snugly when drawn over it. This band should be 
placed at least 2 cm. above the surface of the acid. 

51. In making a preliminary determination of an unknown 
melting-point, the flask is heated cautiously with a free flame 
in such a way that the thermometer rises at the rate of about 
ten degrees per minute. The temperature should be noted at 
which the substance first shows signs of melting and when it has 
completely liquefied. As the thermometer is rapidly rising, this 
result serves only as a guide for the determination of the melting- 
point. When the apparatus has cooled to a number of degrees 
below the temperature at which ‘signs of melting were evident, 
a new tube containing another sample of the substance is intro- 
duced into the apparatus and the melting-point redetermined. 
All melting-point determinations should be made with samples 
which have not been melted. If the thermometer is at a high 
temperature when it is removed from the bath, it should not 
be cooled by placing it in cold water; if this is done the glass is. 
apt to crack. The tube is heated rapidly until the temperature 
is at least ten degrees below that at which the substance melts. 
The flame should be removed and the temperature allowed to 
rise slowly. When the thermometer ceases to rise the flask 
should be heated cautiously so that when the flame is removed 
the temperature does not rise more than one degree. In the case 
of a substance which melts without decomposition, the tempera- 
ture should be allowed to rise at the rate of about two degrees per 
minute for the last five degrees. An endeavor should be made to 
have such control of the bath that the thermometer can 
be forced up a degree at a time. The heating is continued 
until the substance completely runs down the tube as a liquid. 
The point at which this occurs and that at which the substance 
begins to form in droplets should be recorded as the melting- 
point of the sample studied. If these are separated by more 
than one degree, the substance is more or lessimpure. If the sub- 
stance shows signs of contracting or softening before it begins 
to melt, the fact should be noted as it is an indication that it is 
impure. 


LABORATORY METHODS 35 


The determination of the melting-point should be repeated, 
and great care taken to allow the temperature to rise very slowly 
when the substance begins to melt. It may happen that the 
substance melts within one degree, but that it appears to melt 
over a considerable range of temperature on account of the fact 
that the heat has been applied so rapidly that the thermometer 
rises a number of degrees during the time required to melt the 
substance. 

When a substance appears to be pure and gives a sharp melting- 
point, a number of determinations should be made. If these 
give the same result, the melting-point as determined may be 
considered to be thé correct. one. 

If a substance does not melt sharply it should be recrystallized, 
and a second determination made. Asa result of the purification 
the melting-point obtained will probably be higher than before. 
The process is repeated as long as the melting-point rises. 

52. The melting-point determined as indicated is below the 
true melting-point of the substance on account of the fact that 
only part of the mercury is heated to the temperature of the 
melting substance. A close approximation of the true melting- 
point can be found by applying the correction which is found by 
substituting in the formula N(é — t’) 0.000154, in which WN is the 
number of degrees of mercury not heated directly by the acid in 
the bath, ¢ the observed temperature and ?’ the average tempera- 
ture of the stem outside the bath. The correction, which is added 
to the observed temperature, is, in the case of a bath like that 
described, and when the usual form of thermometer which regis- 
ters up to 360° is used, about 1° at 100°, about 2° at 140°, 3° at 
170°, and 6° at 220°. 

53. Determination of. Boiling-points——The determination of 
the boiling-point of a substance is made during the final distilla- 
tion in its purification. If 20 or more grams are distilled, the 
-boiling-point as determined in the apparatus described above 
under distillation, may be considered to be correct. Care must 
be taken, however, not to distil all of the liquid, as when this is 
done the vapor toward the end of the distillation becomes super- 
heated, and the thermometer does not register the true boiling- 
point of the liquid. 

54. If but a small amount of the substance has been prepared, 


36 EXPERIMENTAL ORGANIC CHEMISTRY 


or the boiling-point of a small sample of an organic compound is 
desired, the determination is best made in the manner described 
below, which largely prevents superheating. About 10 cc. of 
the liquid is placed in a 15 ce. flask provided with a thermometer 
the bulb of which is placed just below the side-tube. The flask 
is supported on an asbestos board in which has been carefully 
cut by means of a sharp cork-borer of brass, a hole about 2 em. in 
diameter. The bottom of the flask should fit the hole tightly so 
that the hot gases from the flame can not come in contact with 
the upper part of the flask. 

On account of the smallness of the flask, a large part of the 
thermometer is not heated to the temperature of the vapor and 
a correction should be made for stem exposure as described 
above under the determination of melting-points. In order to 
determine the mean temperature of the stem, a second ther- 
mometer should be attached by means of rubber bands to the 
one used to indicate the temperature of the vapors in the flask. 
The bulb of the second thermometer should be placed at a point 
half way below the upper end of the first thermometer and the 
cork. 

The condenser to be used is determined by the boiling-point 
of the liquid (see §20, page 11). The flask should be heated by a 
free flame of such a size that when it comes in contact with the 
lower part of the flask it furnishes sufficient heat to keep the liquid 
boiling at such a rate that about 0.5 ce. distils per minute. The 
distillation should be stopped when the level of the liquid is 
just below that of the asbestos-board that supports the flask. 

If a very accurate determination of a boiling-point is to be 
made, the substance should be distilled from a tube of such a 
length that the thermometer can be heated by the vapor up to the 
point where the top of the mercury column stands when the sub- 
stance is boiling. When determined in this way no correction 
for stem exposure is necessary. 

55. As the boiling-point varies with the pressure, in recording 
accurately determined boiling-points, both the pressure and the 
temperature are stated. When the determination is made at a 
pressure within 40 mm. of the normal pressure, 760 mm., a cor- 
rection can be applied to the observed reading to reduce the 
boiling-point to that of the substance at the normal pressure. 


LABORATORY METHODS oO” 


This correction is 0.1° for each 2.7 mm. pressure. If the observed 
pressure is less than 760 mm., the correction should be added; if 
greater, it should be subtracted. It is evident that this correc- 
_ tion should not be applied if the substance does not boil sharply 
and if every precaution has not been taken to have a pure sub- 
stance and to eliminate the errors which commonly are present 
in a boiling-point' determination made in the ordinary way. 

56. Determination of Specific Gravity——The determination 
of specific gravity is often made in the identification of organic 
compounds. For this purpose results accurate to 
two units in the third decimal place are sufficient; 
these may be obtained by using as little as 1 cc. of a 
liquid. A convenient form of apparatus for the de- 
termination is described by Mulliken.! It consists 
of a 1 ce. pipette and a glass tube, closed at one end, 
into which the former passes freely (see Fig. 21). 

When the apparatus is weighed, it is stood on the 
pan of an analytical balance and the loop of wire 
is placed over the hook which supports the scale- 
pan. The apparatus is calibrated as follows: The 
pipette and tube are cleaned, dried, and weighed. 
The pipette is next filled to the mark with distilled 
water, the temperature of which is noted; any liquid 
adhering to the outside of the pipette is removed. 
The pipette is put into the tube and the water 
allowed to flow out into the latter. The apparatus 
is welghed again. The increase in weight is the 
weight of water, at the observed temperature, which 4, 9; 
fills the pipette. In determining the specific gravity 
of a substance the pipette is filled with it as before and weighed, 
and the temperature of the liquid is noted. The specific gravity 
is obtained by dividing the weight of the substance by the weight 
of the water. The result obtained is the specific gravity at 
the temperature at which the substance was weighed, com- 
pared with water at the temperature at which it was weighed. 
As it is customary to refer specific gravities to water at 4°, the 
volume of the pipette should be calculated for the weight of 






Tevet |(/| Recaaesacs ata Sa See at RIE 


1 Identification of Pure Organic Compounds, Vol. I. 


38 EXPERIMENTAL ORGANIC CHEMISTRY 


water which it contains. In the following table are given the 
weights of 1 cc. of water at temperatures from 14° to 30°. 


Temp. Temp. Temp. 
14° 0.9993 20° 0.9982 26° 0.9968 
16° 0.9989 ae 0.9977 28° 0.9963 
18° 0.9986 24° 0.9973 30° 0.9957 


The volume of the pipette may be determined by dividing 
the weight of the water by the weight of 1 cc. of water at the 
temperature at which the water was weighed. 

In calculating the specific gravity of a substance the weight 
observed is divided by the volume of the pipette; the result is 
the specific gravity of the substance at the observed temperature 
compared with water at 4°. If the number determined in this 
way for a substance weighed at 18° was found to be 1.365, the 
result would be expressed as 1.36525. 

If a number of determinations of specific gravity are to be 
made, it is advisable to calibrate the pipette to hold 1 cc. If 
this is done the observed weight of the substance which fills the 
pipette is its specific gravity referred to water at 4°. 


THE QUALITATIVE ANALYSIS OF ORGANIC COMPOUNDS 


57. Test for Metallic Elements.—About 0.1 gram of the sub- 
stance is heated in a clean dry porcelain crucible. If it burns 
with a flame or leaves a residue of carbon it is probably organic. 
If the residue is black it should be heated until all the carbon has 
burned off. If the original substance contained a metal there 
will be left in the crucible after ignition either a metal, an oxide, 
oracarbonate. This residue should be identified by the methods 
of inorganic qualitative analysis. Organic compounds which 
leave residues on ignition are usually metallic salts of acids. 

If it is reasonably certain that the substance does not contain 
a metal which is readily reduced by carbon, the ignition can be 
made on a platinum foil. 

If there is doubt as to whether the compound is organic, a 
sample of it can be heated in a hard glass tube with powdered 
copper oxide, and the evolved gas tested for carbon dioxide. If 


LABORATORY METHODS 39 


the substance is volatile it is necessary to place a mixture of it 
and copper oxide in the bottom of the tube and then add enough 
of the oxide to make a layer at least 5 cm. thick. The tube 
is carefully heated, beginning at the point farthest from the bot- 
tom of the tube. 

58. Test for Non-metallic Elements.—The substance to be 
analyzed is first decomposed by heating it with metallic sodium, 
and the resulting mixture, which may contain the following com- 
pounds of sodium, is analyzed: chloride, bromide, iodide, phos- 
phide, sulphide, cyanide, and sulphocyanide. The decomposi- 
tion is accomplished asfollows: A clean, dry 6-inch test-tube is 
supported near the open end in a vertical position by means of 
a clamp and iron stand. A piece of sodium equal in size to a 
cube 3 mm. on each edge is cut and wiped free from oil by means 
of a filter paper. Any deposit on the sodium should be rejected, 
and the piece selected should have clean freshly cut surfaces on 
all sides. The test-tube is warmed, and the sodium dropped in. 
The burner is placed directly under the tube which is heated 
_ until a layer of the sodium vapor about 1 cm. thick is formed. 
The substance to be analyzed is now dropped into the tube, care 
being taken to have it fall directly onto the hot sodium without 
coming into contact with thetube. If the substance 1s a liquid, 
about 3 drops should be used. If it is a solid, a little should 
be taken up on the end of a pen-knife or spatula and dropped into 
the tube; a second portion should then be added. The flame is 
removed immediately, and when the tube is cold, the lower end 
of it should be broken off by tapping the tube with a pestle in a 
clean, dry mortar. If, during the heating, some of the unde- 
composed substance has settled on the upper part of the tube, 
this part should be rejected; only the very end which contained 
the sodium vapor should be used. About 2 cc. of alcohol is then 
added to react with any excess of sodium present. When the 
metal has ceased acting, the contents of the mortar are ground 
with 20 cc. of distilled water, transferred to a small beaker, 
heated to boiling, and filtered. If the decomposition has been 
satisfactorily accomplished a colorless solution is obtained. If 
this is not the case, a second fusion with sodium should be made, 
and great care taken to introduce the substance directly into the 
sodium vapor. 


40 EXPERIMENTAL ORGANIC CHEMISTRY 


Separate portions of the filtrate are tested for non-metallic 
elements as follows: 

Test for Sulphur.—Add to about 2 cc. of a dilute solution of 
sodium hydroxide 2 or 3 drops of a solution of lead acetate. 
To the resulting mixture add about 5 cc. of the filtrate obtained 
as described above. If sulphur is present, black lead sulphide 
will be formed. If but a small amount of sulphur is present, 
a yellow color may be produced without the formation of a pre- 
cipitate. If this is the case, filter the solution after a few minutes, 
and examine the paper for a precipitate of lead sulphide. 

59. Test for Nitrogen.—Boil for a minute about 2 ce. of the 
solution from the fusion with 5 drops of a 10 per cent solution 
of sodium hydroxide and 5 drops of a solution of ferrous sulphate. 
Cool, and add dilute hydrochloric acid drop by drop, until the 
solution becomes acid and the precipitate of ferrous hydroxide 
has dissolved. An excess should be avoided as the reaction 
which takes place if nitrogen is present—the formation of ferric 
ferrocyanide—is more delicate in the absence of an excess of acid. 
If a large amount of acid appears to be necessary, it is evident 
that the original fusion did not completely destroy the organic 
compound. ‘ 

If a blue or green color does not develop on adding the acid, 
a drop of ferric chloride should be added to the tube. It often 
happens that enough ferric ferrocyanide is not formed to produce 
the characteristic blue precipitate; the formation of a clear green 
solution is ample proof of the presence of nitrogen. Such a 
solution usually deposits a blue precipitate on standing. 

60. Test for Halogens.—A preliminary test for halogen should 
be made with some of the original substance. The so-called 
Beilstein test is made as follows: A piece of stout copper wire 
is bent around the end of a lead pencil to make a small loop at 
one end. This end is then heated in a Bunsen flame until it no 
longer imparts a color to the flame. The wire is allowed to cool, 
and the clean end is inserted into the substance to be tested 
if it is a liquid, or a bit of it, if solid, is supported in the loop on 
the wire. It is then put into the flame. If a halogen is present 
a green color is imparted to the flame. The test should be re- 
peated a number of times in order to have the conclusion 
definite. 


LABORATORY METHODS 41 


If a halogen is found to be present the solution obtained from 
the decomposition with sodium should be tested. 

If sulphur and nitrogen have been found to be absent, about 
1 cc. of the solution is acidified with nitric acid, and silver nitrate 
is added. The color of the precipitate formed is an indication 
of the halogen present, provided but one is present. If the pres- 
ence of bromine or iodine is suspected, a second portion of the 
original solution is acidified, and about 2 ec. of carbon disulphide 
is added; chlorine water or a solution of sodium hypochlorite 
is then added, drop by drop. If either sulphur or nitrogen is 
present, it is necessary to boil the original solution for several 
minutes with a few drops of dilute sulphuric acid to remove 
hydrogen sulphide and hydrocyanic acid before the tests for 
the halogens are applied. 

61. Test for Phosphorus.—One cubic centimeter of the original 
solution from the fusion is boiled for 1 minute with 3 cc. of 
concentrated nitric acid. This treatment oxidizes the sodium 
phosphide to sodium phosphate. The presence of the latter is 
tested for by adding to the cooled solution twice its volume of 
ammonium molybdate reagent. The tube is heated to such a 
temperature that it can just be held in the hand, and is then set 
aside. The formation of a yellow precipitate indicates phos- 
phorus, provided arsenic is not present. 


CHAPTER II 


GENERAL PROCESSES: HYDROCARBONS OF THE METHANE 
SERIES 


62. Calibration of a Thermometer.—Calibrate a thermometer 
at 0°, 100°, 183.7°, and 218.1° according to the method described 
in §48, page 31. 


63. Determination of Melting-points.— Determine the melting- 
point of the substances furnished according to the directions 
given in §49-52, pages 32-35. 


64. Fractional Distillation—Read the description of fractional 
distillation in §21-23. Set up an apparatus for distillation like 
that shown in Fig. 2, page 9. Use a 200 ce. distilling flask 
and as receivers three 100 cc. flasks which are labeled, respectively, 
I, 78°-82°; II, 82°-95°; and ITI, 95°-100°. Place 50 ce. of alcohol 
and 50 ec. of water in the distilling flask, and heat the latter with 
a flame of such a size that the liquid distils at the rate of about 
1 drop per second. Collect the part which distils up to 82° 
in the flask numbered I. When this point is reached replace this 
receiver by flask II, and collect the distillate in this flask until 
the thermometer registers 95°. At this point use flask III as the 
receiver. When nearly all the liquid has distilled, pour out the 
small residue from the distilling flask and dry it, or use a clean 
dry flask. Measure in a graduated cylinder the volumes of the 
contents of the three receivers at the end of the first distillation, 
and record the results in your notebook. (See the tabulation 
on page 14.) Place in the distilling flask the liquid in receiver 
I (the first fraction), and distil as before, collecting what boils 
up to 82° in receiver I. When this point is reached, allow the 
distilling flask to cool slightly, and then add to it the contents 
of flask II. Replace the thermometer and distil. Collect what 
passes over below 82° in flask I, and the part which boils between 
82° and 95° in flask II. Remove the flame, and add to the dis- 
tilling flask the contents of flask III. Replace the thermometer 

42 


GENERAL PROCESSES 43 


‘and collect the distillate in the several receivers according to the 
boiling-point. Measure and record the volumes of the three 
fractions at the end of this second distillation. Repeat the 
fractionation a third time and record the volumes of the 
fractions. 


65. Qualitative Analysis of Organic Compounds.—Make 
analyses of the substances furnished, following the directions 
given in §58-61, pages 39-41. 


66. Preparation of Methane from Sodium Acetate; Properties 
of Methane (Suctions 17, 18).—(a) Grind and mix thoroughly 
in a mortar 8 grams of fused sodium acetate! and 8 grams of 
soda-lime.? Transfer the mixture to an 8-inch test-tube pro- 
vided with a rubber stopper fitted with a short piece of glass 
tubing. Connect to the latter by means of a short piece of rubber 
tubing a delivery-tube arranged to collect a gas over water. 
Support the test-tube, by means of a clamp, in such a position 
that the end containing the stopper is slightly lower than the 
other end; this prevents any water given off during the heating 
from running back into the hot tube and cracking it. Heat the 
tube cautiously, keeping the flame in motion, in order to avoid 
local overheating. (Hq.) Collect three 250 cc. bottles of the 
gas. Prepare a mixture of the gas with air by putting into a 
fourth 250 cc. bottle 25 cc. of water; cover the bottle with a glass 
plate, insert it in the pneumatic trough, and pass the gas into 
the bottle until. the water has just been replaced. CauTion.— 
Remove the delivery-tube from the water before the heating of 
the tube is stopped. If during the heating the water begins to 
go back into the test-tube, the breaking of the latter can be pre- 


1 Commercial fused sodium acetate is generally not anhydrous; it is well to 
fuse it before use. If the compound is to be prepared from the hydrated salt 
(CH;COONa.3H.O) proceed as follows: Heat cautiously about 15 grams 
of the crystalline salt contained in an iron pan over a small flame. Stir 
continuously with a glassrod. The salt melts at first in its water of crystal- 
lization; as the dehydration proceeds it solidifies, and, finally, when anhy- 
drous, melts a second time. Care should be taken to avoid heating the 
dehydrated salt much above its melting-point, as it undergoes decomposition 
when strongly heated. 

2 The soda-lime can be replaced by an intimate mixture of 4 grams of 
powdered sodium hydroxide and 4 grams of quicklime. 


44 EXPERIMENTAL ORGANIC CHEMISTRY 


vented by separating the test-tube from the delivery-tube where ~ 
they are joined together. 

(b) Inflammability of methane-——Drop a lighted match into 
one jar of the gas. Is soot produced? Why? (Kgq.) What is 
the color of the flame? 

(c) Explosive mixture of methane and air.—Light the mixture 
of methane and air. Explain the difference between the results 
obtained in this case and in (b). (Egq.) Calculate the relation 
between the volume of methane and the volume of oxygen in 
the gas exploded. State the volumes which interact according 
to the equation for the reaction. 

(d) Methane and bromine.—Add one drop of bromine to a 
bottle of the gas. This can be done conveniently by placing a 
pipette, made from a piece of glass tubing drawn down to a 
small bore at one end, into a bottle of bromine and placing the 
finger over the end of the pipette, which is then withdrawn. 
Cover the bottle with a glass plate, and allow it to stand for a 
few minutes until the bromine has vaporized. Drop a lighted 
match into the bottle. (#q.) When the reaction is complete 
breathe sharply across the mouth of the bottle, and test the gases 
in the bottle with a piece of moist blue litmus paper. 

(e) Methane and an oxidizing agent—Make a dilute solution 
of potassium permanganate by dissolving a crystal of the salt 
in one-half a test-tube full of water. Add the solution to a 
bottle of methane, replace the cover, and shake. Explain. 


Notrs.—(a)! Soda-lime is preferably used in experiments of this type 
rather than sodium hydroxide, as the latter rapidly attacks glass at the tem- 
perature at which the reaction takes place. 

(b) The methane prepared in this way is not pure; it contains small 
amounts of substances (acetone, for example) which impart a yellow color 
to the flame. The reaction should be brought about at the lowest tempera- 
ture at which it takes place, in order to reduce the amount of by-products 
formed. Pure methane burns with a flame that is only slightly luminous. 

(c) The violence of the explosion is reduced by the fact that the oxygen 
which reacts with the hydrocarbon is diluted with nitrogen. A mixture of 
one volume of methane and two volumes of oxygen explodes with violence 
when ignited. 

(e) This test is of value in distinguishing hydrocarbons of the methane 
series from other hydrocarbons which rapidly reduce an aqueous solution of 


1 The letters used in the notes refer to the paragraphs under these letters 
in the description of the experiments. 


GENERAL PROCESSES 45 


potassium permanganate. If reduction occurs it is due to the fact that 
the methane is impure. 


67. Preparation and Properties of Ethane: Grignard Reaction. 
—(a) Into a dry 50 cc. Erlenmeyer flask fitted by means of a 
cork to a return condenser, place 2 grams of magnesium powder 
and a small crystal of iodine. Add through the condenser 5 cc. 
of ethyl bromide and 10 cc. of ether dried over sodium. In 
about 15 minutes when reaction ceases (Hq.) replace the condenser 
by a two-holed stopper carrying a small separatory funnel and a 
delivery-tube to collect a gas over water. Add water to the flask 
drop by drop, through the funnel. (Kq.) Collect two 250 ce. 
bottles of the gas. 

(b) Inflammability of ethane-—Drop a lighted match into one 
bottle of the gas and note the color of the flame. 

(c) Ethane and oxidizing agents.—Test the second bottle of 
gas to determine whether ethane can be readily oxidized. (See 
experiment 66e, page 44.) 


Notr.—(a) A trace of iodine is usually added to the mixture of halide 
and magnesium in effecting a Grignard synthesis, in order to hasten the 
reaction. The reaction is similar to that by which methane is formed 
from methyl iodide and magnesium. (See end of SecTIon 17.) 

68. Preparation and Properties of Di-isoamyl: Wurtz Syn- 
thesis.—(a) To 20 grams of isoamyl bromide contained in a 
dry 100 ce. round-bottomed flask add 5 grams of sodium cut into 
about six pieces. Connect the flask with a piece of glass tubing 
about 3 feet long, to serve as a reflux condenser, and allow it to 
stand over night. Connect the flask with an air condenser, 
and distil with a smoky flame which is kept constantly in motion 
to avoid local overheating. (Hq.) Redistil slowly the distillate 
from a small flask, and save and weigh the fraction which boils 
at 158°-161° Isoamyl bromide boils at 118.6° and di-isoamyl 
at 159.5°. CautTion.—Read carefully §41, page 27. The flask 
contains unused sodium, and water should not be put into it. 
Add portions of 5 cc. of alcohol from time to time until the evolu- 
tion of hydrogen ceases, and there is enough of the liquid to make 
a thin paste of it with sodium bromide; then pour the contents 
of the flask cautiously into an open vessel containing water. Do 
not pour water into the flask. Great care should be taken in 
the disposal of sodium residues which should be always treated 


46 EXPERIMENTAL ORGANIC CHEMISTRY 


in the manner just described; serious explosions and accidents 
frequently happen as the result of a lack of proper precautions. 

Calculate the theoretical yield from the isoamyl bromide used 
and the percentage obtained in the experiment. 

(b) Di-itsoamyl and bromine—Add 2 drops of bromine to 
about 2 cc. of di-isoamyl. Breathe across the tube. Is there 
any evidence of substitution? Heat the contents of the tube 
to boiling and test for hydrobromic acid as before. (£q@.) 

(c) Di-tsoamyl and sulphuric acid—Add 2 ce. of the hydro- 
carbon to about 5 cc. of concentrated sulphuric acid, and shake 
well. Allow the tube to stand a few minutes and observe the 
contents. Do the two liquids mix? 

(d) Di-isoamyl and nitric acid.i—Repeat experiment (c) above 
using concentrated nitric acid instead of sulphuric acid. Record 
the results obtained. 


Norres.—(a) In carrying out the Wurtz synthesis the reaction is often 
brought about in a solvent; the halide, or mixture of halides, is diluted with 
about twice its volume of ether which has been dried over sodium. The 
preparation described above should yield from 7 to 8 grams of the slightly 
impure hydrocarbon. 

(c and d) Concentrated sulphuric acid and nitric acid are valuable agents 
for distinguishing between the paraffin hydrocarbons and many other classes 
of compounds which dissolve in these reagents. 


69. Composition of Kerosene (Section 24).—Distil about 
25 cc. of kerosene, using a small flask and a condenser. (See Fig. 
2, page 9.) CautTion.—See that all corks fit tightly and that 
the receiver is not near a flame. Note the temperature at which 
the liquid begins to drop freely from the condenser and when the 
last part is distilling over. Compare the boiling-points obtained 
with those of the paraffin hydrocarbons, and state what com- 
pounds are present in the sample studied. 


Notr.—Crude petroleum is separated into various commercial products 
according to the specific gravity of the distillates. These products are not 
carefully fractionated and are mixtures. (See SzecTion 28.) 


70. Properties of Gasoline and Kerosene (Sections 26 to 
28).—(a) Kerosene and acids and alkalies—In separate test- 
tubes shake about 5 cc. of distilled kerosene with 10 ce. each of 
concentrated nitric acid, concentrated sulphuric acid, and a 
dilute solution of sodium hydroxide. Note if heat is evolved 


ae ae. Pee 


ee 


Oe ee 


GENERAL PROCESSES 47 


or if there is a change in color. Record your observations and 
conclusions. Gasoline behaves in a similar way. 

(6) Solubility of kerosene —Test the solubility of about 2 ce. 
of kerosene or 1 gram of paraffin in water, ether, alcohol, and 
ligroin or petroleum ether. Caution.—Volatile inflammable 
liquids such as ether, alcohol, and petroleum ether should not be 
heated over a free flame. They can be heated conveniently by 
immersing the vessel containing them in boiling water. 

(c) Gasoline and bromine.—To 10 ce. of gasoline contained 
in a dry test-tube add 2 cc. of a 5, per cent solution of bromine 
in carbon tetrachloride. Divide the mixture into two portions; ° 
place one in your desk in the dark, and the other in direct sun- 
light. After a few minutes compare the two tubes. Breathe 
across the tubes. Explain the difference observed. (Eq.) 

(d) Flash-point of gasoline.—Pass a burning match over a few 
drops of gasoline placed on a watch-glass. What statement can 
you make in regard to the flash-point of gasoline? 

(e) Flash-point of kerosene-—This experiment should be car- 
ried out in aplacewherethereisnodraft. Support a plain beaker 
of 50 cc. capacity in a 100 cc. beaker by means of a triangle made 
of copper wire, or a piece of pasteboard in which a hole has been 
cut just large enough to allow the body of the small beaker to 
pass. Fill the smaller beaker with kerosene and the larger 
beaker with water. In each case the level of the liquid should 
be within one-half inch of the top of the beaker. CautTion.— 
Have an asbestos board or a watch-glass at hand with which to 
smother the flame in case the kerosene takes fire during the ex- 
periment. Insert a burning match into the kerosene. What can 
you say of the flash-point of kerosene? Place the apparatus on a 
wire gauze, and heat cautiously with a flame, the tip of which 
should be about 3 inches below the gauze. Insert into the kero- 
sene the bulb of a thermometer, which should be supported by a 
clamp. The temperature of the oil should rise not faster than 2° 
per minute. Attach by means of a rubber tube to the gas-cock 
a blowpipe or a piece of glass tubing drawn out to afine opening. 
The gas should be regulated to produce a flame about one-half 
inch in length. When the temperature of the kerosene reaches 
35°, pass the flame quickly over the surface of the oil, taking care 
not to touch it. Repeat the test for every degree rise in tempera- 


48 EXPERIMENTAL ORGANIC CHEMISTRY 


ture. Record the temperature at which the vapor of the oil 
ignites; this is made evident by a slight flash which is more or 
less difficult to see. As soon as the flash-point has been observed, 
extinguish the flame under the apparatus. If the kerosene does 
not flash before 48°, turn out the flame and consult the in- 
structor. Compare your results with the flash-point of kerosene 
required by law (Section 28) 


Notr.—(a) Owing to the cracking of the paraffin oils in their distillation, 
samples of the commercial products from petroleum often contain small 
quantities of hydrocarbons which react with sulphuric acid and with nitric 
acid. When these impurities have been removed by repeated shaking with 
concentrated sulphuric acid, the resulting paraffin hydrocarbons show their 
characteristic inertness. 


CHAPTER III 
UNSATURATED HYDROCARBONS 


71. Preparation of Ethylene from Alcohol (Srcrion 29).— 
Weigh directly into an 8-inch test-tube 4 grams of phosphorus 
pentoxide. Connect the test-tube by means of a closely fitting 
cork with a reflux air-condenser; immerse the tube in cold water, 
and pour 5 cc of ethyl alcohol slowly into the condenser. The 
alcohol should be added cautiously in small portions and the 
test-tube shaken under water, as much heat is evolved when 
alcohol comes in contact with phosphorus pentoxide. Support 
the test-tube at an angle of about 45° with the table by means of 
a clamp, and connect it with a delivery-tube arranged to collect 
a gas over water. Heat the tube carefully until the mixture 
becomes homogenous; then more strongly until a steady stream 
of gas is evolved. Collect three 250 ce. wide-mouthed bottles 
of the gas, and prepare an explosive mixture of ethylene and air. 
This can be done by placing 20 cc. of water in a 250 cc. wide- 
mouthed bottle, covering the latter with a glass plate, inverting 
in a pneumatic trough, and displacing the water by ethylene. 
See the following experiment. 

Notrre.—When sulphuric acid, which is commonly used as a dehydrating 
agent in the preparation of ethylene, is employed, the reaction takes place at 
a temperature very near that at which the alcohol chars; as a consequence, 
carbon often separates, the mixture froths badly, and sulphur dioxide and 
carbon dioxide are formed. The apparatus for the preparation in this way 
is described under ethylene bromide (experiment 137, page 103). 

72. Properties of Ethylene (Section 30).—(a) Inflammability 
of ethylene.—Throw a lighted match into a bottle of ethylene. 
In order to facilitate the removal of the gas, a stream of water 
should be poured into the bottle as the gas burns. Note the 
color of the flame, and compare with results obtained when 
methane was burned. (Explain.) 

(b) Explosive mixture of ethylene and air.—Throw a lighted 
match into the bottle containing the mixture of ethylene and air. 

4 49 


50 EXPERIMENTAL ORGANIC CHEMISTRY 


(c) Ethylene and bromine-—Hoopv.—Add 2 drops of bromine to 
a bottle of the gas. (See experiment 66d, page 44.) Replace 
the glass cover and shake. When the color of bromine has 
disappeared, observe carefully the contents of the bottle. Are 
there drops of an oil present? (Hq.) Test the gas in the bottle 
with moist blue litmus paper. Compare the results with those 
obtained with methane. 

(d) Ethylene and oxidizing agents —Dissolve a small crystal 
of potassium permanganate in about 20 cc. of water, and add 
a little of the solution to a bottle of the gas. Replace the cover 
and shake. Explain the value of the test, and compare the re- 
sults with those obtained with methane. (See experiment 66e, 
page 44.) 

(e) Test for unsaturated compounds in coal gas——Collect over 
water a bottle of illuminating gas. Add a dilute solution of 
potassium permanganate in portions of 5 cc. to the bottle and 
shake. What conclusions can be drawn as to the presence of 
unsaturated hydrocarbons in illuminating gas? What are the 
chief constituents of coal gas? Of water gas? Of what value are 
the unsaturated hydrocarbons in these gases? 


73. Preparation of Ethylene from Ethylene Bromide (SrecTIon 
29).—Into a 6-inch test-tube place about 2 cc. of ethylene bro- 
mide, 2 ce. of alcohol, and about 0.5 gram of sheet zinc. Connect 
the tube with a delivery tube, warm gently until reaction begins, 
and collect a test-tube full of the gasover water. (H#q.) Burn 
the gas. (Kq.) 


74. Properties of Unsaturated Hydrocarbons (Srction 35).— 
(a) Amylene and bromine.—Dissolve 1 ce. of amylene in 5 ce. 
of carbon tetrachloride, and add gradually, as long as an evident 
reaction takes place, a solution prepared by dissolving 2 ce. of 
bromine in 50 cc. of carbon tetrachloride. (Hq.) Test for 
evolved hydrobromic acid by breathing across the mouth of the 
tube. 

(b) Amylene and oxidizing agents.—Shake a few drops of amy- 
lene with about 20 cc. of a dilute solution of potassium per- 
manganate prepared by dissolving a crystal of the salt in one- 
‘half a test-tube full of water. (H¢.) 


en ” 


.UNSATURATED HYDROCARBONS 51 


75. Preparation and Properties of Acetylene (Sections 38 
to 40).—(a) Support a dry 200 cc. distilling flask by means of a 
clamp, and connect the side-arm of the flask with a delivery- 
tube arranged to collect a gas over water. Fit a dropping funnel 
into the neck of the flask by means of a cork. Place in the flask 
about 10 grams of calcium carbide, and let water fall very slowly, 
drop by drop, from the funnel onto the carbide. (#yq.) Fill 
four 250 cc. bottles with the gas generated, rejecting the first 
bottle-full collected. Why? Prepare an explosive mixture of 
acetylene and air by putting 15 cc. of water into a wide-mouthed 
bottle, covering the bottle with a glass plate, inverting the bottle 
in the pneumatic trough, and displacing the water by acetylene. 
CautTion.—Do not let acetylene escape freely into the air; the 
gas has an unpleasant odor and is poisonous. 

(b) Inflammability of acetylene—Throw a lighted match into 
a bottle of the gas. Is much soot deposited? Note the luminos- 
ity of the flame and compare your results with those obtained 
when methane and ethylene burned. | 

(c) Explosive mixture of acetylene and air.—Throw a lighted 
match into a bottle containing the mixture of acetylene and air. 
How does the explosion compare in intensity with those obtained 
with methane and ethylene? 

(d) Acetylene and oxidizing agents.—Apply the potassium per- 
manganate test for unsaturation. (See experiment 66¢, page 44.) 

(e) Acetylene and bromine.—Add to a bottle of the gas about 
5 drops of bromine. Replace the cover of the bottle and shake. 
If the color does not disappear in a minute, add to the bottle a 
few cubic centimeters of a dilute solution of sodium hydroxide 
and shake. When the color has disappeared, observe the con- 
tents of the bottle carefully. (Eq.) Note the odor of the prod- 
uct formed. How could acetylene be obtained from this com- 
pound? © (Eq.) 

(f) Test for the triple bond.—Test a bottle of the gas for a 
compound containing a triple bond, using an ammoniacal solu- 
tion of cuprous chloride which can be made as follows: Heat 
together in a test-tube over a flame, a few pieces of copper oxide 
and metallic copper with about 10 cc. of dilute hydrochloric 
acid (sp. gr. 1.1). When the solution becomes colorless, cool, 
decant off about 5 cc. of the liquid and add ammonia until the 


52 EXPERIMENTAL ORGANIC CHEMISTRY 


solution is alkaline. Add this solution to a bottle of the gas; 


cover the bottle and shake. (Kq.) 


Nores.—(a) The acetylene prepared in this way from commercial cal- 
cium carbide contains impurities, such as hydrogen sulphide and phosphine. 
If the gas is to be used to prepare other compounds, it should be purified 
by passing it through a wash-bottle containing a solution of mercuric chlo- 
ride in hydrochloric acid. 

(c) It is easy to obtain an explosive mixture of air and acetylene as the 
proportion of acetylene in such mixtures may vary between wide limits, 
namely, from 3 to 82 per cent by volume. In the case of methane and 
ethylene, the limiting volumes are from 5 to 13 per cent of the former and 
from 4 to 22 per cent of the latter. 

(f) This test applies only to compounds containing the C=CH group; 
the compounds must contain a hydrogen atom linked to a carbon atom which 
is joined to a second carbon atom by a triple bond. | 


———— 


a 


CHAPTER IV 
ALCOHOLS 


76. Properties of Methyl Alcohol (Srction 49).—(a) Inflam- 
mability of methyl alcohol.—Pour about 1 cc. of methyl alcohol 
into an evaporating dish and apply a burning match. (£¢.) 
Note the appearance of the flame. 

(b) Solubility of methyl alcohol.—Test the solubility of methyl 
alcohol in water, ether, ethyl alcohol, petroleum ether, and ben- 
zene. Use about 1 cc. of the alcohol in each test. 

(c) Methyl alcohol as a solvent.—Test the solubility of anhy- 
drous calcium chloride and sodium chloride in methyl] alcohol. 

(d) Methyl alcohol and sodium.—Add a piece of sodium the 
size of a small pea to 5 cc. of methyl alcohol. (Kq.) 


77. Tests for Methyl Alcohol.—(a) Methyl salicylate-—Mix 
together in a test-tube about 0.2 gram of salicylic acid, 1 ce. of 
concentrated sulphuric acid, and 1 cc. of methyl alcohol, and 
warm gently. Note and describe the odor. The compound 
formed is the methy] ester of a salicylic acid, HO.CsH4.COOCH:3. 

(b) Formaldehyde (Section 143).—Dissolve 5 drops of methyl 
alcohol in 3 cc. of water. Wind a piece of stout copper wire 
around a lead pencil so that a closely coiled spiral about 2 cm. 
in length is formed; leave about 20 cm. of the wire to serve as a 
handle. Heat the spiral in the upper part of a Bunsen flame, 
and plunge it while red hot into the solution of methyl! alcohol. 
Withdraw the spiral, cool the liquid under running water, and 
heat again with the hot spiral. In this way the methyl alcohol 
is oxidized by the hot copper oxide formed on the wire. Note the 
odor of the liquid while hot. Cool the liquid, add 2 drops of a 
0.5 per cent solution of resorcin and pour the resulting mixture, 
slowly so the two liquids do not mix, down the side of an inclined 
test-tube containing about 5 cc. of concentrated sulphuric acid. 


78. Preparation of Ethyl Alcohol by Fermentation (Srcrion 
52).—(a) Dissolve 40 grams of commercial anhydrous glucose in 
53 


o4 EXPERIMENTAL ORGANIC CHEMISTRY 


350 cc. of water in a 500 ec. bottle. Add one-fourth of a yeast 
cake ground to a smooth paste with 50 cc. of water, and about 
0.5 gram of Witte’s peptone.! Close the bottle with a rubber 
stopper through which passes one end of a glass tube bent in two 
right angles to form three sides of a rectangle. The other end of 
the tube passes to the bottom of a test-tube which is held in 
place by means of cork along the side of which a groove is cut to 
allow the escape of gas. The test-tube is one-half filled with a 
solution of barium hydroxide. By using the apparatus arranged 
in this way, any gas evolved must pass through the solution of 
barium hydroxide before it escapes. Mark the bottle with your 
name by means of a label, and set it in a warm place (about 30°). 
Examine the contents of the bottle at the next laboratory exer- 
cise. Has the amount of yeast increased in quantity? What gas 
has been evolved? 

The product obtained is a dilute solution of ethyl alcohol which 
contains small quantities of other substances. The alcohol 
should be separated, and the amount formed in the reaction 
determined as follows: Decant through a folded filter-paper, 
taking care not to disturb the sediment of yeast, about 250 cc. 
of the solution. While waiting for the solution to filter, weigh 
to centigrams a clean dry 100 cc. flask, around the neck of 
which has been pasted a narrow strip of paper to serve as a ref- 
erence mark. Fill the flask up to the mark with distilled water, 
and weigh again. Place‘exactly 200 cc. of the filtered solution 
from the fermentation into a 500 cc. distilling flask, neutralize, 
using litmus paper, with a dilute (10 per cent) solution of sodium 
hydroxide, and distil into the weighed flask until the liquid fills 
it exactly to the mark. (For the arrangement of the distilling 
flask and condenser see Fig. 2, page 9.) Weigh the flask and 
contents. Save the distillate for a later experiment. Calculate 
the specific gravity of the distillate, which contains all the alcohol 
that was present in 200 ec. of the product of fermentation. By 
reference to a table of the specific gravity of aqueous solutions of 
alcohol, calculate the weight of alcohol obtained from the 40 
grams of glucose used in the experiment. What was the total 

1 Yeast requires for its growth certain salts which are present in Witte’s 
peptone. If the latter is not available it may be replaced by 20 cc. of a 


solution made by dissolving 10 grams each of potassium phosphate, magne- 
sium chloride, and calcium nitrate in 1 liter of water. 


ee 


Powe ees ee eee 


Al) eo ee ee Te 


mipnis 


ae 


CRN ioe Sega ta lp alan 





ALCOHOLS 595 


volume of the solution fermented? Calculate the theoretical 
amount of alcohol obtainable from 40 grams of glucose and the 
percentage of this (the yield) obtained in your experiment. 

Write an equation for the reaction by which alcohol is formed 
from glucose. Why is the solution kept in a warm place during 
fermentation? Why is the solution neutralized before distil- 
lation? How could you determine whether an acid volatile 
with steam was formed during the fermentation? 

(b) Place the dilute alcohol obtained in (a) above in a 200 cc. 
distilling flask and distil off slowly about 50 ce. Add to this 
distillate solid anhydrous potassium carbonate as long as the salt 
dissolves. 

(c) Test the product obtained in (a) or (6) by the iodoform 
test. (Experiment 81b, page 57.) 


Notss.—(a) If very accurate results are desired it is necessary to take 
into account the temperature of the water in standardizing the contents of 
the flask, and to note the temperature of the dilute alcohol. The specific 
gravities of aqueous solutions of aleohol vary with the temperature. In the 
analysis of beverages for alcohol the specific gravity is usually determined 
by means of a hydrometer or a Westfall balance. 

(b) The alcohol obtained in this way still contains water. It may be 
rendered anhydrous by a second treatment with potassium carbonate and 
with lime as described in experiment 80 below. The soluble monatomic 
alcohols can be separated from not too dilute solutions in water by saturat- 
ing them with potassium carbonate. 


79. Properties of Ethyl Alcohol (Sections 53, 57).—(a) In- 
flammability of alcohol_—Touch a lighted match to a few drops of 
alcohol on a watch-glass. 

(b) Solubility of alcohol—Test the solubility of alcohol, using 
about 5 ce. in each experiment, in water, benzene, kerosene, and 
concentrated sulphuric acid. | 

(c) Test for water in alcohol—Add to 5 ce. of commercial 95 
per cent alcohol about 1 gram of anhydrous copper sulphate, 
which can be prepared by cautiously heating the crystalline salt 
over a free flame in an evaporating dish. Note the change in 
color. Explain. Repeat the experiment, using absolute alcohol. 
For what purpose could this reaction be used? 

(d) Place a erystal of potassium permanganate in about 5 ce. 
of 95 per cent alcohol. Repeat, using absolute alcohol. 

(e) Alcohol and sodium.—Add to about 5 cc. of absolute al- 


{ 


56 EXPERIMENTAL ORGANIC CHEMISTRY 


cohol a piece of sodium the size of a pea. Test the evolved gas. 
(Hq.) Evaporate the solution on a water-bath. Dissolve the 
resulting product in water and test the solution with litmus 
paper. (Eq.) 

(f) Alcohol and hydrobromic acid.—Place 2 cc. of alcohol and 
10 ce. of hydrobromic acid (sp. gr. 1.49) into a test-tube supported 
in a clamp and provided with a delivery-tube. (See Fig. 18, 
page 30.) Let the second end of the tube pass to within 1 inch 
of the bottom of a test-tube which is placed in a beaker containing 
cold water. Heat the solution of alcohol and acid carefully 
until about 5 ce. of liquid have distilled over. Examine the dis- 
tillate. (Eq@.) 

(g) Alcohol and acetyl chloride—Hoopv.—In making the fol- 
lowing test take care that the mouth of the test-tube is directed 
away from you. Add acetyl chloride cautiously, drop by drop, 
from a pipette to 2 cc. of alcohol in a test-tube, which is kept 
cool by immersion in water, as long as reaction takes place. 
Note the gas evolved. (Hq.) Pour the contents of the tube 
cautiously into 5 cc. of cold water, and shake. Note the odor of 
the product. 

(h) Alcohol and acetic anhydride-—Cavution.—The reaction 
which takes place in this experiment is apt to occur with viclence. 
The experiment should be performed under the hood. In a test- 
tube add 2 cc. of alcohol to 2 ce. of acetic anhydride. Is there 
any evidence of action? Support the tube in a vertical posi- 
tion by means of a clamp. Place a glass rod into concentrated 
sulphuric acid, and then rub it against the neck of the bottle to 
remove the drop that adheres. Put the rod with the trace of 
acid into the mixture of alcohol and anhydride. Wait until the 
mixture boils. (Hgq.) Add the product to 5 cc. of cold water. 
If the ester does not separate, saturate the aqueous solution with 
sodium chloride. Note the odor of the product formed. 

(1) Oxidation of alcohol—Heat together about 1 cc. of alcohol, 
5 ec. of a solution of potassium bichromate, and 5 ec. of dilute 
sulphuric acid. Note the change in color and the production 
of a characteristic odor. Write the equations for the reac- 
tion, including the change which takes place in the potassium 
bichromate. 


ALCOHOLS od 


Notr.—(h) Sulphuric acid serves as a valuable catalytic agent in bringing 
about a reaction between alcohols and acid anhydrides. 


80. Preparation of Absolute Alcohol (Section 53).—(a) In a 
500 cc. flask add quicklime broken into small lumps to 200 cc. 
of 95 per cent alcohol until the pieces just project above the sur- 
face of the liquid. Connect the flask with a reflux condenser 
($38, page 25), and heat to boiling on a water-bath for 1 hour. 
Do not place the flask in the boiling water. Remove the bath, 
and when the alcohol ceases boiling arrange the condenser for dis- 
tillation (Fig. 2, page 9). Distil from the water-bath and collect 
the distillate in a filter-bottle, which is attached to the con- - 
denser by means of a cork stopper. In order to protect the 
alcohol, which is hygroscopic, from the moisture in the air, con- 
nect to the side-arm of the bottle by means of a piece of rubber 
tubing a small drying tube containing calcium chloride. Collect 
the first 10 cc. in a small dry flask, and then adjust the filter- 
bottle to receive the rest of the distillate. Keep the absolute 
alcohol in a stoppered bottle for future use. Why is the first 
part of the distillate rejected? Give a reason for the fact that 
absolute alcohol can not be obtained from a mixture with water 
by fractional distillation. What substance other than quicklime 
could be used for freeing alcohol from water? Could phosphorus 
pentoxide, concentrated sulphuric acid, or calcium chloride be 
used? State a reason for your answer in each case. 

(6) Test portions of the first distillate, and of the absolute 
alcohol obtained for water with anhydrous copper sulphate and 
with potassium permanganate. (See experiment 79c and d, page 
55.) 


81. Tests for Ethyl Alcohol (Srcrions 57, 214).—(a) Ethyl 
acetate—Warm gently together in a test-tube about 1 cc. of al- 
cohol, 1 cc. of glacial acetic acid, and 2 cc. of concentrated sul- 
phuric acid. Note the odor. (Eq.) 

(b) Iodoform test—Add 5 drops of alcohol and about 1 ce. of 
a dilute solution (10 per cent) of sodium hydroxide to 5 ce. of 
water in a test-tube. Add to the mixture, drop by drop, a solu- 
tion of iodine in potassium iodide! until a faint yellow color per- 


1 This solution is made by dissolving 1 part of iodine and 5 parts of potas- 
sium iodide in 15 parts of water. 


58 EXPERIMENTAL ORGANIC CHEMISTRY 


sists after the solution is shaken. Heat the test-tube until it 
feels warm to the hand (about 60°). If a precipitate does not 
separate at once set the tube aside for a few minutes. Note the 
odor and color of the precipitate. 


Norrs.—(a) Tests which are based on the recognition of odors are not 
reliable for the absolute identification of compounds. Whenever possible 
the compound to be identified is converted into a solid substance, which 
possesses a definite melting-point. For a test for ethyl alcohol based on 
this principle see The Identification of Pure Organic Compounds, by S. P. 
Mulliken, Vol. I, page 168. 

(b) A number of substances yield iodoform when treated with iodine 
and sodium hydroxide. Isopropyl alcohol and acetone give the test imme- 
diately in the cold. 


82. Preparation of Allyl Alcohol (Srcrions 69, 80).—(a) Into a 
500 cc. distilling flask, which is connected with a condenser and 
receiver, place 50 grams of oxalic acid, 200 grams of glycerol and 
0.5 gram ammonium chloride. Fit into the neck of the flask by 
means of a stopper a thermometer so placed that the bulb is 
near the bottom of the flask. Heat over a wire gauze cautiously. 
Carbon dioxide is rapidly evolved and the thermometer registers 
about 130° for some time. As the temperature rises the evolu- 
tion of gas slackens and finally ceases. When the temperature 
reaches 195°, the receiver, which contains a dilute aqueous solu- 
tion of formic acid, is changed. At about 200° carbon dioxide is 
again evolved and water and allyl alcohol distil over. When the 
thermometer registers 260°, the distillation is stopped. 

The distillate which contains the allyl alcohol is redistilled 
slowly from a flask fitted in the usual way with a thermometer. 
When the temperature reaches 103°, test from time to time about 
2 cc. of the distillate for allyl alcohol by saturating it with solid 
anhydrous potassium carbonate. When an oil no longer sepa- 
rates, stop the distillation. Combine the products and saturate 
the solution with solid anhydrous potassium carbonate. Sepa- 
rate the layer of oil, and redistil. The allyl alcohol obtained in 
this way boils at 87°-97° and contains water. Weigh the product 
obtained and note its odor. The alcohol can be used for the ex- 
periments described below. In order to obtain the alcohol in 
dry condition, it should be placed in a fiask and treated with 
barium oxide until the pieces project from the surface of the 
liquid. The flask should then be connected with a return con- 


ALCOHOLS 59 


denser and allowed to stand over night. It is necessary to use 
the condenser, as the heat evolved in the union of the water and 
oxide often heats the alcohol to boiling. The alcohol obtained 
directly by distillation from the barium oxide boils at 96°-98°. 
The yield of alcohol is about 40 per cent of the theoretical. 

Allyl alcohol boils at 96.6° and has the specific gravity 0.872 
at 0°. 


83. Properties of Allyl Alcohol (Srction 69).—(a) Test the 
solubility of allyl alcohol in water. 

(b) Allyl alcohol and bromine.—Hoop. —To 1 cc. of allyl al- 
cohol add bromine, drop by drop, as long as reaction occurs. 
(Eq.) 

(c) Allyl alcohol and acetyl chloride-——Hoop.—Add acetyl 
chloride. cautiously (see experiment 79g, page 56) to 2 ce. of 
allyl alcohol until reaction ceases. (Kq.) Pour the product into 
5 ec. of cold water. Shake and note the odor. 

(d) Application of the iodoform reaction to allyl alcohol.— 
Determine whether allyl alcohol gives the iodoform reaction. 
Carry out the test as in experiment 81b, page 57. 

(e) Allyl alcohol and oxidizing agents—Hoopv.—Heat a mix- 
ture of 1 drop of the alcohol, 5 cc. of a solution of potassium 
bichromate, and 5 cc. of dilute sulphuric acid. Note the odor 
of acrolein (Section 153), which is the aldehyde obtained by the 
oxidation of allylaleohol. (Hq.) Clean the tube under the hood. 


84. Properties of Glycerol (Srctions 73, 74, 153).—(a) Solu- 
bility of glycerol.Test the solubility of glycerol in water, alcohol, 
ether, petroleum ether, and benzene. 

(b) Conversion of glycerol into acrolein.—Cover the bottom 
of a test-tube with powdered acid potassium sulphate and then 
add about 5 drops of glycerol. Heat strongly and note the 
odor. (EKq.) 

(c) Test for glycerol with Pras bead.—Prepare a borax bead 
in the usual way. Place the bead when cold into an aqueous 
solution of glycerol, and then insert into a Bunsen flame. Note 
the color of the flame. Glycerol liberates boric acid from borax. 

(d) Test for glycerol with a solution of borax.—Make a dilute 
solution (about 1 per cent) of borax in a test-tube. Add 2 drops 
of a phenolphthalein solution. What is the color? Why? 


: 


60 EXPERIMENTAL ORGANIC CHEMISTRY 


Add now a neutral aqueous solution of glycerol slowly until the 
color is destroyed. Heat the solution to boiling and then cool. 

(e) Test for glycerol by the preparation of glyceryl tribenzoate.— 
To obtain a solid derivative of glycerol the melting-point of 
which can be determined proceed as follows: Place in a small 
flask 3 drops of glycerol, 1 cc. of benzoyl chloride, and 10 cc. 
of a 10 per cent solution of sodium hydroxide. Cork the flask, 
and shake vigorously for 10 minutes. At the end of this time 
the compound formed will adhere to the sides of the flask. De- 
cant off the liquid, and wash with cold water. Pour off as much 
as possible of the latter, and add 10 ec. of alcohol. Heat on 
the steam-bath, and filter the hot solution into a small flask. 
Add 2 cc. of water, stopper the flask, and shake it vigorously 
under running water. Filter off the crystals by suction, and wash 
them with a mixture of 5 cc. of alcohol and 2 cc. of water. Let 
the product, which is the tribenzoate of glycerol, (CsHsCOO)3C3Hs, 
dry in the air, and then determine its melting-point, which is 
71°-72°. If the compound does not melt sharply, recrystallize 
it from alcohol and water as before. 


Notrs.—(b) If larger quantities of glycerol are used the acid potassium 
sulphate should be replaced by phosphorus pentoxide; with this reagent 
frothing is avoided and no sulphur dioxide is formed. 

(d) Other polyatomic alcohols behave as glycerol does in this test. 
Ammonium salts cause the disappearance of the color of the phenol- 
phthalein, but the color is not restored in this case by boiling. 

(e) Alcohols in general are converted into esters of benzoic acid when 
treated with benzoyl chloride as described in the test. (Baumann and 
Schotten reaction, Section 463.) It should be noted that glycol gives an 
ester which melts at 71°; it is evident, therefore, that the test is not appli- 
cable in the presence of glycol. 


CHAPTER V 
ACIDS 


85. Formation of Formic Acid by the Oxidation of Methyl 
Alcohol (Section 80).—Place in a 100 ce. distilling flask, 5 grams 
of powdered potassium bichromate, 20 cc. of water, and 5 cc. of 
concentrated sulphuric acid. Cool the flask, and add slowly with 
shaking 2 ec. of methyl alcohol drop by drop, keeping the flask 
under water. Place the flask for about 10 minutes in a beaker 
containing boiling water. Distil off, using a condenser, about 10 
cc. of liquid. Apply to the distillate tests described in experi- 
ment 87b andcbelow. Write equations for all reactions involved. 


86. Preparation of Formic Acid from Oxalic Acid (Section 
80).—Into a 250 ce. distilling flask, provided with a condenser 
and receiver, put 20 grams of anhydrous glycerol and 20 grams of 
oxalic acid. Close the flask by a cork carrying a thermometer 
which is so placed that the bulb is below the surface of the 
glycerol. Heat cautiously with a small flame. Carbon dioxide 
is given off at about 80°. Maintain the temperature at 105°- 
110° until the evolution of gas has slackened. Cool the contents 
of the flask to about 60°, add 20 grams more of oxalic acid, and 
heat as before. Repeat the addition of oxalic acid until 80 
grams in all of the acid have been used. After the last portion 
of the acid has been added, allow the temperature to rise to 115°. 
A dilute aqueous solution of formic acid is obtained. (q.) 


87. Properties of Formic Acid (Section 80).—(a) Odor of 
formic acid.—Note the odor of the solution obtained in experi- 
ment 86 above, and test the solution with blue litmus paper. 

(b) Reduction of silver formate.—Neutralize 2 cc. of the dilute 
solution of formic acid with ammonia. Add a few drops of a 
solution of silver nitrate, and warm carefully. (Hq.) 

(c) Reduction of mercuric formate-—Shake for about 1 minute 
2 cc. of the distillate with 0.2 gram of mercuric oxide. Filter 

61 


62 EXPERIMENTAL ORGANIC CHEMISTRY 


the solution and heat it to boiling. The mercuric formate first 
formed is reduced to mercurous formate, and finally to mercury. 
(Hq.) This is a valuable test for formic acid. 

(d) Reduction of mercuric chloride by formic acid.—To 5 ce. 
of the distillate add 2 ec. of a solution of mercuric chloride and 
heat. The mercuric chloride is reduced to mercurous chloride. 
(Eq.) 

(e) Decomposition of formic acid by sulphuric acid.—To 2 ec. 
of the distillate add 2 cc. of concentrated sulphuric acid slowly 
and heat gently. (Kq.) Apply a flame to the liberated gas. 
If an inflammable gas is not obtained, repeat using 0.5 gram of 
sodium formate. 

(f) Oxidation of a formate-——Neutralize 1 cc. of the distillate 
with a dilute solution of sodium hydroxide. Add, drop by drop, 
a dilute (rose-colored) solution of potassium permanganate. 
(Hq.) What is the significance of the result when compared 
with the action of unsaturated hydrocarbons with potassium 
permanganate? (See experiment 72d, page 50.) 

(g) Salts of formic acid.—Dilute what is left of the distillate 
with an equal volume of water and divide it in two portions; 
boil one for about 5 minutes with an excess of lead oxide, and the 
other with copper oxide. Filter the solutions while still hot and 
set aside to crystallize. 


88. Formation of Acetic Acid from Ethyl Alcohol (SrctTion 
85).—To 15 grams of coarsely powdered potassium bichromate 
contained in a 200 cc. round-bottomed flask, add a mixture of 
15 grams of concentrated sulphuric acid and 10 ce. of water. 
Set the flask on a sand-bath and connect it with a reflux con- 
denser through which a rapid stream of water is passing. Add 
through the condenser slowly, in portions of 0.5 cc., 3 ce. of 
alcohol. Shake after each addition and wait until the vigorous 
reaction which takes place subsides before another addition of 
alcohol is made. When all the alcohol has been added, heat to 
boiling for 15 minutes. Change the condenser and distil off 
about 10 ce. (Kq.) Observe the odor of the solution (see note) 
and test it for acetic acid by experiment 91a and b below. 

Notr.—There is usually present in the distillate ethyl acetate and alde- 


hyde, both of which have a characteristic odor. A mixture of potassium 
bichromate and sulphuric acid (chromic acid) is an excellent oxidizing agent 


ACIDS 63 


to use in the preparation of acetic acid by oxidation, since acetic acid 
is not readily oxidized by chromic acid. 


89. Preparation of Glacial Acetic Acid (Srction 83).—Melt 
cautiously in an iron dish about 50 grams of anhydrous sodium 
acetate. Grind the salt to a coarse powder in a mortar; weigh 
40 grams of the salt and place it in a 200 cc. distilling flask. Add 
cautiously through a funnel, keeping the flask cold by immersion 
in water, 25 cc. of concentrated sulphuric acid. Place a ther- 
mometer in the flask in order to determine the temperature of 
the vapor. Connect with a condenser and receiver, and distil 
off the acetic acid. Weigh the acid obtained. Calculate the 
theoretical amount which can be obtained from 40 grams of 
sodium acetate, and the percentage yield of the experiment. 
CautTion.—Glacial acetic acid causes painful blisters when left 
in contact with the skin. 


90. Properties of Acetic Acid (Smction 87).—(a) Solubility of 
acetic acid.—Test the solubility of acetic acid in water, alcohol, 
ether, and benzene. Place about 10 cc. of the acid obtained in a 
test-tube surrounded by chipped ice and water. Insert a ther- 
mometer into the acid. If crystals do not form, scrape the side 
of the tube with a glass rod. If the acid freezes, remove the tube, 
stir with the thermometer, and note the temperature when the acid 
is about one-fourth melted.? Pure acetic acid melts at 16.7° and 
boils at 119°. One per cent of water lowers the melting-point 
about 2.1°. 

(b) Acetic acid and oxidizing agents—Determine whether 
acetic acid reduces solutions of potassium permanganate, silver 
nitrate, and mercuric chloride. Compare the results with those 
obtained with formic acid. (Experiment 87, page 61.) 

(c) Add a few crystals of chromic acid to a mixture of 5 cc. 
of glacial acetic acid and 2 cc. of water. Heat to boiling. Is the 
chromic acid reduced? 

(d) Formation of verdigris Stand a piece of copper foil in 
a small beaker containing acetic acid; a part of the foil should 


1 Tf the anhydrous salt is not available, dehydrate the crystalline salt for 
this experiment according to the directions given in experiment 66a, page 
43. 

2 If the acid prepared does not freeze, determine the melting-point, as 
described above, of a sample of glacial acetic acid. 


64 EXPERIMENTAL ORGANIC CHEMISTRY 


be under the liquid and a part exposed to the air. Examine 
the foil at the next exercise. What is formed? 


91. Tests for Acetic Acid (Section 89).—(a) Formation of basic 
ferric acetate—Add a few drops of a solution of ferric chloride 
to a solution of sodium acetate. Note the color. Heat the solu- 
tion to boiling. The neutral ferric acetate is converted into a 
basic acetate. (Hgq.) In using this test for the free acid it must 
first be neutralized with sodium hydroxide. 

(b) Formation of ethyl acetate—Repeat the test involving the 
formation of ethyl acetate given in experiment 81a, page 57. 

(c) Conversion of acetic acid into acetanilide-—Place in a dry 
test-tube 0.6 gram of anhydrous sodium acetate, 0.25 cc. of 
concentrated sulphuric acid, 1 cc. of aniline. The substances used 
should be measured accurately. Close the mouth of the tube 
with a cork bearing a piece of glass tubing about 2 feet long. 
Support the tube in a vertical position and heat it so the contents 
boil gently for about 1 hour. Cool, dissolve the product in 25 ce. 
of boiling water, filter hot, and set aside to crystallize. Deter- 
mine the melting-point of the crystals. Acetanilide melts at 
67: 

Notr.—(c) The identification of a substance is best accomplished by 
converting it into a solid which has a definite melting-point and can be readily 
purified. In the case of acetic acid and its homologues the anilides serve this 


purpose well (Section 416). They are formed as the result of the elimina- 
tion of water from the acid and aniline: 


CH;COOH +- CeH:NH2 = CH;CONHCe¢H; + H,O 


If the acid to be identified is dissolved in water it is neutralized with 
sodium hydroxide and the solution evaporated to dryness. The salt is 
cautiously heated over a free flame to drive out the water of crystallization; 
it is then heated with aniline and enough concentrated sulphuric acid to set 
free the organic acid. When salts are used the reaction is as follows: 


CH;COONa + CeHsNHe.H:SO, = CH;CONHCcHs + NaHSO, + HO 


92. Preparation and Properties of Soap: Saponification of 
Fat (Srction 96).—(a) Melt 35 grams of lard in a casserole and 
add slowly, with constant stirring, 10 cc. of a strong solution of 
sodium hydroxide made by dissolving 1 part of sodium hydroxide 
in 1 part water. When an emulsion has formed, heat the mix- 
_ ture cautiously over a low flame, stirring it until it begins to boil. 


ACIDS 65 


Continue the heating until the mixture becomes homogeneous. 
If spattering can not be avoided, heat the casserole on a steam- 
bath. Pour the soap into a beaker, and allow it to stand for 
several days. The chief constituents of lard are the glyceryl 
esters of palmitic, stearic, and oleic acids. Write equations for 
the reactions which take place when these three substances are 
heated with sodium hydroxide. 

(b) Test for free alkali in soap.—Determine whether the soap 
prepared in (a) above contains free alkali, as follows: Dissolve 
a small piece of the soap in cold water and test the solution with 
a solution of phenolphthalein. 

(c) Hydrolysis of soap.—Shake vigorously a piece of Ivory 
soap about the size of a large pea with 10 cc. of cold water. Test 
one-half of the solution with a solution of phenolphthalein. 
How do you explain the difference between the result of this 
experiment and that obtained with the soap you prepared? 
Heat to boiling the other half of the solution of Ivory soap 
and add phenolphthalein. Explain and write equations for 
the reaction. 

(d) Soft soap.—Cut the soap you prepared into thin shavings 
and heat it with 400 cc of water until it dissolves. Divide the 
product into four parts. Put aside one of these and allow it to 
cool. Describe the properties of the soft soap. 

(e) Salting out of soap.—Precipitate one portion of the solu- 
tion by adding slowly, with stirring, an equal volume of a satu- 
rated salt solution. Filter off the precipitate and save the filtrate 
for another experiment. Wash the precipitate with 50 cc. of 
saturated salt solution, let it drain thoroughly, and finally spread 
it on a watch-glass to dry. Test the soap for free alkali as in (0) 
above. From what organic compound has the soap been sepa- 
rated by this treatment? 

(f) Solubility of soap.—Test the solubility of the purified soap 
in water, in alcohol, and ether. This can be done most readily 
by shaking pieces of the soap with about 15 cc. of each of the 
solvents, filtering, and evaporating the solvents on a water-bath. 
If there is any residue from the ether, test it to determine whether 
it is soap, or fat which has not saponified. 

(g) Action of hard water and soap.—To determine the action 


of hard water on a solution of soap, add to small portions of the 
5 


66 EXPERIMENTAL ORGANIC CHEMISTRY 


solution prepared in (d) above, solutions of calcium chloride and 
magnesium sulphate. (Kq.) Test the solubility of the precipi- 
tates in water. Explain the difference between the action of 
sodium chloride and calcium chloride on a soap solution. Did 
you note any difference in the action of the two salts on a dilute © 
solution of soap? What chemical compounds may be present in 
natural hard water? 

(h) Isolation of fatty acids from soap.—To the remainder of 
the solution prepared in (d) above, add dilute hydrochloric acid 
as long as a precipitate is formed. Of what does this precipitate 
consist? (Hgqs.) Filter and wash with cold water; drain thor- 
oughly and spread the precipitate on a watch-glass to dry. Test 
the solubility of the precipitate in water, sodium hydroxide (£q.), 
ether, and alcohol. Place a small piece of the precipitate in a 
test-tube one-half full of water; heat to boiling and shake. 
Describe the appearance. Cool and shake. What is the effect 
of hot water on the acids? On the basis of their solubility, 
state how you could separate into its constituents a mixture 
which contained fat, fatty acids, and soap. 

(t) Test for unsaturated acids in soap.—Dissolve about 1 gram 
of the acids obtained in experiment (hk) above in 5 cc. of carbon 
tetrachloride and add, drop by drop, a solution of bromine in 
carbon tetrachloride. Explain. (£q.) : 

(7) Identification of glycerol in the product of the hydrolysis of 
fat—The presence of glycerol can be shown as follows: Neu- | 
tralize with dilute hydrochloric acid about 100 ce. of the solution 
reserved in experiment (e) above; filter, evaporate the filtrate to 
dryness, and stir the residue of salt and glycerol with about 20° 
ee. of alcohol. Decant off the liquid through a filter and evapo- 
rate on the steam-bath. A sample of impure glycerol will be: 
left. Prove the presence of glycerol by applying two of the 
tests given in experiment 84, page 59. | 


Notrs.—(a) If one precipitation does not free the soap from alkali, 
redissolve it and precipitate again. 

(e) Ether dissolves fat but does not dissolve soap; this solvent can be 
used, therefore, to determine the presence of unsaponified fat in a sample - 
of soap. er 


93. Preparation and Properties of Oxalic Acid (Szctions 106, 
108).—(a) Heat on the steam-bath in an open 500 ce. flask 120° 


ACIDS 67 


grams of concentrated nitric acid (sp. gr. 1.42) and 20 grams of 
cane-sugar. As soon as brown fumes begin to be evolved, place 
the flask in a hood, and let it stand until the rapid evolution 
of oxides of nitrogen ceases. Evaporate on the steam-bath 
until the volume of the liquid is reduced to about 30 cc. Set 
aside to crystallize. Filter off the acid through a funnel provided 
with a perforated plate, using no filter-paper. Dissolve the crys- 
tals in the smallest amount of boiling water possible, and set 
the solution aside to crystallize. Oxalic acid dissolves in 10.46 
parts of water at 14.5°. Weigh the product obtained. 

(b) Action of heat on oxalic acid.—Heat about 1 gram of oxalic 
acid in a dry test-tube; continue the heating after the water of 
crystallization has been driven off. Describe the result. Oxalic 
acid, (COOH)>:.2H,0, melts at 99°; the anhydrous acid sublimes 
at 150°-180°. 

(c) Change of a formate to an oxalate—Heat in a dry test- 
tube about 1 gram of sodium formate. (Hq.) Apply a flame 
to the gas evolved. Test the residue for an oxalate according 
to experiment 94 c below. | 

(d) Potassium tetroxalate——Dissolve 5 grams of oxalic acid in 
30 cc. of hot water. Neutralize exactly one-fourth of this solu- 
tion carefully with potassium hydroxide; combine the solutions 
and set aside to crystallize. (Hq.) When cold, filter off the 
salt. Dissolve a little of the salt in water, and try its effect on 
an iron-rust stain, also on a spot made with an iron ink and an 
ink made from an aniline dye. 

(e) Potassium ferric oxalate-—Add to a solution of ferric chlo- 
ride a solution of potassium oxalate until a clear green solution 
is formed. (Kq.) Mboisten a piece of paper with the solution. 
_ Test the paper for a ferrous salt by putting on it a drop of potas- 
sium ferricyanide. Expose a piece of the paper to direct sunlight 
for 1 minute and test again for a ferrous salt. 


94. Tests for Oxalic Acid and Oxalates (Sections 106, 108).— 
(a) Oxalic acid and sulphuric acid.—Heat about 2 grams of oxalic 
acid with about 5 cc. of concentrated sulphuric acid. (£q@.) 
Pour some of the gas formed into a test-tube containing a solu- 
tion of barium hydroxide, and shake. Ignite the gas which is 
produced in the reaction. How could you prepare carbon mon- 
oxide free from carbon dioxide by making use of this decomposi- 


68 EXPERIMENTAL ORGANIC CHEMISTRY 


tion? What other acid yields carbon monoxide when heated 
with sulphuric acid? 

(b) Silver oxalate-——In a test-tube neutralize a solution of 
oxalic acid with ammonia; if a slight excess of ammonia is added, 
boil the solution until it is neutral to litmus. Cool and add a 
solution of silver nitrate. A precipitate of silver oxalate is 
formed. (Eq.) Heat to boiling. Compare the results with 
those obtained with formic acid (experiment 87b, page 61). 

(c) Precipitation of calccwm oxalate-——To a solution of oxalic 
acid add ammonia in slight excess, and then a solution of calcium 
chloride. (Hq.) Test the solubility of the precipitate in a 
solution of acetic acid and in dilute hydrochloric acid. How 
would calcium carbonate act when treated with acetic acid? 

(d) Reducing action of oxalic acid—To a solution of oxalic 
acid or an oxalate add dilute sulphuric acid and a solution of 
potassium permanganate. (qs.) 

(e) Repeat (d), using a solution of potassium bichromate in 
place of one of potassium permanganate. (qs.) 


CHAPTER VI 


ETHERS, ESTERS, AND ANHYDRIDES 


95. Preparation of Ether from Alcohol (Section 115).—(a) 
CautTion.—Kther is very inflammable and very volatile; as its 
vapor readily ignites, vessels containing ether should not be 
brought near a flame or allowed to stay in a warm place. Place 
50 cc. of ethyl alcohol in a 500 ce. distilling flask and add slowly, 
with constant shaking, 50 cc. of concentrated sulphuric acid. 
Close the neck of the flask with a two-holed stopper bearing a 
thermometer and a dropping funnel (Fig. 16, page 27), both of 
which reach to the bottom of the flask.! Place the flask on a 
sand-bath and connect it by means of a tightly fitting stopper 
with a long condenser, through which a rapid stream of cold 
water is passing. Use as a receiver a filter-bottle which is con- 
nected with the condenser by a tightly fitting stopper. Attach 
to the side-arm of the filter-bottle a long rubber tube, which 
extends almost to the floor. This tube serves to conduct the 
vapor of the ether, which is very heavy, away from any flames 
present on the desk. Heat the contents of the flask slowly. 
When the temperature reaches 140°, and ether distils over, add 
through the funnel 100 ce. of alcohol, allowing the latter to drop 
at about the same rate as that at which the ether distils (about 
2 drops per second). During the entire time the temperature of 
the mixture in the flask should be maintained at 140°-145°. 

Take the receiver away from the immediate vicinity of any 
flames, and transfer the contents to a separatory funnel. Shake 
the ether with about one-half its volume of a dilute solution of 
sodium hydroxide. Draw off the lower aqueous layer, which 
should still be alkaline, and shake the ether with about one- 
half its volume of a saturated solution of common salt. Draw 
off the lower layer, and run the ether into a small distilling flask. 


1 Tf a dropping funnel is not available or if the tube of the funnel is not 
long enough, arrange the apparatus as described in §40, page 27. 
69 


70 EXPERIMENTAL ORGANIC CHEMISTRY 


Add anhydrous calcium chloride (about one-fourth the volume 
of the ether). Close the neck of the flask with a stopper bearing 
a small drying tube containing calcium chloride, and place over 
the side-arm a cork which has been bored one-half way through 
its length, the hole having a diameter equal to that of the side- 
arm of the flask. Set the flask aside for at least an hour. Re- 
place the drying tube by a thermometer and distil the ether 
directly from the calcium chloride, using a water-bath. Collect 
the distillate in a receiver as described above. Record the boil- 
ing-point and the weight of the product obtained. Ether boils 
at 35°. Write equations for the reactions which take place when 
alcohol is treated with sulphuric acid, and when the product of 
this reaction is heated with alcohol at about 140°. What would 
happen if in the experiment the temperature were allowed to 
rise as high as 180°? 

(b) Absolute ether—The ether prepared as described in (a) 
above contains traces of alcohol and water. In order to prepare 
ether free from these substances proceed as follows: Shake 
200 ce. of commercial ether with about 20 cc. of a dilute solution 
of sodium hydroxide. Draw off the aqueous layer and shake the 
ether three times with a saturated solution of sodium chloride, 
using about 25 cc. each time. Transfer the ether to a bottle and 
add about 20 grams of anhydrous calcium chloride. Place a 
drying tube containing anhydrous calcium chloride in the neck 
of the bottle, and allow the ether to stand over night. Decant — 
the ether into a dry bottle and add about 5 grams of sodium in 
the form of a wire or thin shavings. Insert a calcium chloride 
tube in the neck of the bottle and allow it to stand until the evo- 
lution of hydrogen ceases. The sodium is soon covered with a 
coating of hydroxide and ceases to act. This coating can be 
removed by pressing upon the shavings of sodium with a stout 
glass rod, or fresh pieces of the metal may be added from time to 
time. For most purposes the ether purified in this way can be 
used without distillation; it can be carefully decanted from the 
solid substances present. In order to redistil it, the ether is 
transferred to a clean dry flask containing about 1 gram of sodium 
shavings and distilled from a water-bath, taking the precautions 
described in (a) above, and using a carefully dried condenser and 
receiver. The first few cubic centimeters which distil should be 


ETHERS, ESTERS, AND ANHYDRIDES 71 


rejected, as they contain the moisture present in the condenser 
tube and receiver. How could you determine whether the 
sample of ether purified contained alcohol? 


Notr.—(a) The ether prepared in this way contains water, alcohol, and 
‘sulphur dioxide, which is formed as the result of the reduction of sulphuric 
acid by the alcohol or carbon which separates. Ether is less soluble in water 
which is saturated with sodium chloride than in pure water. It is often 
advisable when extracting an aqueous solution with ether to saturate the 
solution with salt, in order to avoid loss of ether. 


96. Properties of Ether (Sections 115 to 119).—(a) Volatility 
of ether.—Place a few drops of ether in the palm of your hand 
and breathe sharply across it. Explain the result. 

(b) Inflammability of ether.—Place a few drops of ether on a 
watch-glass and apply a lighted match. 

(c) Explosive mixture of ether and air.—Hold for about 5 
seconds the neck of an open bottle containing ether over an 
empty wide-mouthed 250 cc. bottle, and then drop a lighted 
match into the latter. 

(d) Solubility of ether in water.—Test roughly the solubility of 
ether in water as follows: Into a 100 ce. flask place 5 cc. of ether 
and add 40 ce. of water. Close the flask witha stopper and shake 
vigorously. Add water in portions of 5 cc. and shake each time, 
until the ether has completely dissolved. State the solubility 
you find as the result of your experiment. 

(e) Solubility of water in ether—Shake 10 cc. of ether with 
10 ce. of water. Decant off the ether through a dry filter-paper 
into a dry test-tube. Test the filtered ether for water by means 
of anhydrous copper sulphate. (See experiment 79c; page 55.) 
Is water soluble in ether? 

(f) Solubilities of ether—Test the solubility of ether in an 
equal volume of alcohol, benzene, petroleum ether, dilute hydro- 
chloric acid, and a solution of sodium hydroxide. 

(g) Solubility of ether in sulphuric acid—Add very cautiously 
to 2 ce. of ether about 5 ce. of concentrated sulphuric acid. The 
tube should be shaken under water to keep the mixture cold. 
Is ether soluble in concentrated sulphuric acid? Pour the mix-— 
ture slowly into a test-tube containing cracked ice. Are two 
layers formed? Explain. (See Srcrion 117.) 

(h) Reaction between ether and sulphuric acid.—Repeat ex- 


72 EXPERIMENTAL ORGANIC CHEMISTRY 


periment (g), but warm the mixture gently over a free flame before 
it is poured onto the ice. Are two layers formed? Explain. 

(2) Hther and sodiwm.—Add a shaving of sodium to about 
5 ec. of absolute ether. If a gasis evolved, wait until the evolu- 
tion ceases and add a fresh piece of sodium. Explain the result. 
If anhydrous ether is not available the experiment can be per- 
formed with ordinary ether, but a number of additions of sodium 
will be necessary before the metal does not react with the liquid. 
Why? 

(7) Decomposition of ether by hydriodic acid.—Mix in a test- 
tube, kept cold by immersion in water, 1 cc. of ether and 3 cc. 
of hydriodic acid (sp. gr. 1.7). Fit the tube by means of a cork 
to a delivery-tube bent at a right angle. (See Fig. 18, page 30.) 
The end of the tube should extend nearly to the bottom of a 
test-tube which is placed in cold water. Heat the mixture of acid 
and ether carefully. When about one-third of the liquid has 
distilled over, add a little water to the contents of the cold tube 
and shake. Are there two liquids? Is one heavier than water? 


(£q.) 


97. Preparation of a Mixed Ether: Isoamyl Ethyl Ether (Sxc- 
TION 116).—Place 50 grams of isoamyl alcohol in a 200 cc. round- 
bottomed flask provided with a reflux condenser. Add slowly 
through the condenser 6 grams of sodium cut in small pieces. 
The alcohol may be heated slightly to hasten the reaction. When 
all the sodium has dissolved, add cautiously through the con- 
denser, as the reaction is apt to be a violent one, 30 grams of 
ethylbromide. Heattoboilingforlhour. (Hq). Distil directly 
from the flask, using a water condenser, and collect the distillate 
in the following fractions: 80°-110°, 110°-114°, .114°-120°, 
120°-130°. Fractionate twice. (See §21-23, and experiment 
64, page 42.) Redistil the portion boiling at 110°-114°, and 
collect and weigh the part which distils at 111°-113°. Deter- 
mine the specific gravity of your product (§56, page 37), and 
determine whether it dissolves in concentrated sulphuric acid. 
Calculate the percentage yield of ether obtained from the ethyl 
bromide used. The yield in the experiment should be about 
50 per cent. 

Isoamyl ethyl ether boils at 112°, and has the specific aes 
0.764 at 18°. 


ETHERS, ESTERS, AND ANHYDRIDES 73 


Notr.—An excess of alcohol is used in the experiment to facilitate the 
reaction between it and sodium. Sodium isoamylate is a solid which is 
soluble in isoamyl alcohol. The sodium and ethyl bromide are used in the 
proportion of one atomic weight of the former to one molecular weight of the 
latter. 


Actp ANHYDRIDES 


98. Preparation and Properties of Acetic Anhydride (SrcT1ons 
120, 121).—-(a) Place 50 grams of freshly fused sodium acetate! 
in a 250 ce. distilling flask. Connect the flask with a condenser 
and a receiver, using for the latter a distilling flask which is 
fitted tightly to the condenser by means of a stopper. Protect 
the inside of the flask from moisture by connecting a drying tube 
to the side-arm of the receiver. Insert in the neck of the flask 
a cork bearing a separatory funnel which contains 40 grams of 
acetyl chloride. Immerse the flask in cold water and add about 
one-half of the acetyl chloride very slowly. The liquid should 
not be allowed to get hot enough to boil. Disconnect the flask 
from the condenser and shake it cautiously, while it is still in the 
water. Replace the condenser and add the rest of the chloride. 
If any liquid distils over during the addition of the acetyl chloride, 
it should be returned to the distilling flask. Replace the separa- 
tory funnel by a cork and distil, keeping the flame in motion to 
avoid local over-heating. Add about 2 grams of fused sodium 
acetate to the receiver and distil; note the boiling-point of the 
liquid, and weigh the product obtained. (Kq.) Calculate the 
theoretical yield, and the percentage of this obtained in the 
experiment. If the substances from which the anhydride is 
prepared are not brought together in the proportions represented 
by the chemical equation, from which substances should the 
theoretical yield be calculated? In the above experiment which 
substance is used in excess? Why? 

Acetic anhydride boils at 138°. The yield should be from 35 
to 40 grams. 

(b) Acetic anhydride and water—Add about 1 ce. of acetic 
anhydride to 5 ce. of water. Do the two liquids mix? Shake 
the test-tube vigorously and finally warm gently. (Hq.) 


1 For the preparation of fused sodium acetate see experiment 66a, page 
43. 


74 EXPERIMENTAL ORGANIC CHEMISTRY 


(c) Acetic anhydride and sodium hydroxide—Shake 2 cc. of 
the anhydride with 5 ce. of a solution of sodium hydroxide. (£q.) 

(d) Acetic anhydride and alcohol.—Repeat experiment 79h, 
page 56. 

(e) Identification of acetic anhydride-—Add cautiously 2 ce. 
of acetic anhydride to 2 cc. of aniline, and heat the mixture to 
boiling. Pour the product while still hot into about 20 cc. of 
cold water. Shake vigorously, decant off the water and wash 
twice with cold water. Dissolve the product in boiling water, 
avoiding an excess of the solvent. Filter hot through a fluted 
filter-paper, and cool the solution in running water. Filter off 
the crystals by suction ($12, page 7), dry them on a porous 
plate, and determine their melting-point. If the compound does 
not melt sharply, it should be recrystallized from boiling water. 

Acetanilide, the product of this reaction, melts at 116°, boils 
at 304°, and crystallizes from hot water in colorless prisms. 
(See note below and Sxrction 416.) 


Nortes.—(a) The first distillate is redistilled from a small amount of 
sodium acetate in order to convert any unchanged acetyl chloride into 
anhydride. 

(b, c, and d) These reactions apply in general to anhydrides and are 
useful in their identification. The determination of the physical properties 
of the acids or esters formed is often made in the identification of anhy- 
drides. Sulphuric acid is a valuable catalytic agent in the reaction which 
takes place between alcohols and anhydrides. 

(e) The chemical reaction in this test. is analogous to that which takes 
place between an anhydride and ammonia: 


(CH;CO).0 + 2NH; = CH;CO.NH, + CH;COONH, 


Aniline is related to ammonia; its formula is NH,CsHs. The reaction with 
acetic anhydride takes place according to the following equation: 


(CH;CO).0 + 2NH.CsH; = CH;CO.NHCeHs + CH:COONH;CeHs 


In the case of ammonia, acetamide is formed; the product with aniline is 
acetanilide. The second substance formed is the aniline salt of acetic acid; 
this is soluble in water and is readily removed when the product of the 
reaction is crystallized. The preparation of anilides in this way from acid 
anhydrides is often effected in the identification of anhydrides. The 
anilides are solids, which can be readily purified; as a consequence, an iden- 
tification can be accomplished with a very small amount of a substance. 


99. Preparation of. Succinic Anhydride (Srctrion 122).— 
Hoopv.—Heat to boiling for about one-half hour, in a dry round- 


ETHERS, ESTERS, AND ANHYDRIDES 75 


bottomed flask provided with a return condenser, a mixture of 
10 grams of phosphorus oxychloride and 15 grams of succinic 
acid. It is advisable to use a return condenser like the one illus- 
trated in Fig. 15, page 26. 

When the flask is cold, add 50 cc. of acetone and heat on the 
steam-bath until the solid has dissolved. Filter hot and set 
aside to crystallize. Filter off the crystals by suction ($12, page 
7), and wash them with a few cubic centimeters of cold acetone. 
Weigh the product and determine its melting-point. Calculate 
the percentage yield. 

Succinic anhydride melts at 120°; it may be recrystallized 
from hot chloroform, in which it is difficultly soluble, or from 
acetone. 


Notr.—Phosphorus oxychloride is used as a dehydrating agent in this 
preparation. The reaction takes place according to the following equation: 


2(CH2COOH):2 + POC]; = 2(CH.CO).0 + HPO; + 3HCl 


ESTERS 


100. Preparation of Potassium Ethyl Sulphate (Srction 127). 
—(a) Pour into asmall flask 20cce. of ethylalcohol, and add slowly 
with constant shaking 10 cc. of concentrated sulphuric acid. 
Connect the flask with a reflux condenser and heat in a boiling 
water-bath for one-half hour. Cool the liquid and pour it slowly 
into 200 ce. of cold water. The solution contains ethyl sulphuric 
acid, alcohol, and sulphuric acid. The acids are separated by 
making use of the fact that barium ethyl sulphate is soluble in 
water and barium sulphate is insoluble. Add to the solution, 
with constant stirring, small quantities of barium carbonate! as 
long as carbon dioxide is evolved. Filter in a porcelain funnel, 
and wash the precipitate twice with about 20 cc. of hot water. 
The filtered solution contains barium ethyl sulphate. Write 
equations for all the reactions. Test 5 cc. of the solution for 
barium in the usual way. (Eq.) Test the solution forasulphate. 
Result? Heat about 5 cc. of the solution with about 1 cc. of 
dilute hydrochloric acid. (q.) 

(b) Conversion of barium ethyl sulphate into potassium ethyl 


1 If barium carbonate is not available, calcium carbonate may be used. 


76 EXPERIMENTAL ORGANIC CHEMISTRY 


sulphate.—Heat the rest of the solution of barium ethyl sulphate 
to boiling and add a solution of potassium carbonate until the 
solution is slightly alkaline. (Hq.) Filter hot, wash the precipi- 
tate twice with a small amount of hot water, and evaporate the 
filtrate to crystallization (see §9, page 6) on the steam-bath. 
When cold, filter off the crystals and wash them with a little 
cold alcohol; dry on a porous tile. The salt can be recrystallized 
from boiling alcohol. 


101. Preparation of Ethyl Acetate from Alcohol and Acetic 
Acid (Section 128).—Mix in a dry 200 ce. distilling flask 50 
grams of alcohol, 60 grams of glacial acetic acid, and 4 ce. of 
concentrated sulphuric acid. Cover the side-arm of the flask 
with a cork bored half way through its length. Connect the 
flask with a reflux condenser, and heat to boiling for 30 minutes. 
(See Fig. 14, page 25.) At the end of this time, arrange the 
apparatus for distillation, using a water condenser and having a 
thermometer to record the temperature of the vapor. Distilinto 
a flask; when the temperature registers 100°, collect separately 
about 1 cc. of the distillate and add it to about 5 cc. of water. 
If the mixture does not separate into two layers, stop the dis- 
tillation. Shake the distillate in the flask with 30 cc. of water, 
and add solid sodium carbonate until a drop of the ester is neutral 
to moist litmus paper. Transfer to a separatory funnel, draw 
off the water, and shake the ester twice with a saturated solution 
of calcium chloride, using 50 cc. each time. Draw off the ester 
into a distilling flask, add about one-fourth its volume of an- 
hydrous calcium chloride, close the flask and cover the side-arm 
with corks, and let stand for at least 1 hour. Distil from a 
water-bath. Note the boiling-point and the weight of ester ob- 
tained, and calculate the percentage yield from the acetic acid 
used. Why from the acetic acid? 

Ethyl acetate boils at 77°, has the specific gravity of 0. 99281°° me 
and is soluble in 17 parts of water at 17.5°. The yield should be 
80 to 85 per cent of the theoretical. 


Notr.—The sulphuric acid used in the preparation serves as a catalytic 
agent. The amount of alcohol used is that equivalent to the acid (equal 
molecular proportions) plus that which combines with the sulphuric acid to 
form ethyl hydrogen sulphate. The ester obtained in the first distillation 


ETHERS, ESTERS, AND ANHYDRIDES U2 


contains alcohol and acetic acid. The former is removed by shaking with 
calcium chloride, and the latter by treatment with sodium carbonate. 

102. Formation of Ethyl Acetate from Acetyl Chloride and 
from Acetic Anhydride.—Consult your notes on experiments 
79g and h, page 56. If you have not carried out the experi- 
ments, do so now. 


103. Properties of Ethyl Acetate (Srction 130).—(a) Hydroly- 
sis of ethyl acetate——Place 25 cc. of ethyl acetate and a solution 
of 14 grams of sodium hydroxide in 200 cc. of water in a round- 
bottomed flask connected by a tightly fitting cork to a reflux 
condenser. Place the flask in boiling water, and heat until 
liquid ceases to flow back from the condenser (about three- 
fourths of an hour). Transfer the liquid to distilling flask, and 
distil off 50 cc. into a small flask. Reserve for future study the 
contents of the distilling flask. Add solid potassium carbonate 
to the distillate in small portions. Close the flask and shake it. 
Repeat the addition of the salt until a part of it remains undis- 
solved. Pour the two layers into a separatory funnel, run off. 
the lower aqueous solution, and shake again with a small quantity 
of dry potassium carbonate. Place the alcohol in a small distill- 
ing flask, add about one-fourth its volume of anhydrous copper 
sulphate, and allow the mixture to stand about 15 minutes with 
occasional shaking. Distil the alcohol on a water-bath directly 
from the flask, and note its boiling-point. Apply the iodoform 
test to a few drops of the alcohol (experiment 81b, page 57). 

Make the original aqueous solution obtained in the hydrolysis 
strongly acid with dilute sulphuric acid (Kq.), and distil over 
50 cc. What does the distillate contain? Prove your conclu- 
sions by a suitable test. Explain how the procedure used in 
this experiment serves to separate an acid and an alcohol. Is 
the process one of general applicability? 

(b) Ethyl acetate and concentrated sulphuric acid.—Add gradu- 
ally with constant shaking, and keeping the mixture cool by 
running water, 2 cc. of ethyl acetate to 4 cc. of concentrated sul- 
phuric acid. Pour the solution very slowly, keeping the tube 
cold, into 10 cc. of cold water. Will this test distinguish an 
ester from an ether? From a saturated hydrocarbon? 

Repeat the experiment, but heat the mixture for a minute 
at about 100° before adding the solution to water. (q.) 


78 EXPERIMENTAL ORGANIC CHEMISTRY 


(c) Ethyl acetate and hydriodic acid.—Repeat experiment 96), 
using ethyl acetate in place of ether. For what is the test used? 
Will alcohol give a positive result? 


104. Preparation of Isoamyl Acetate from Sodium Acetate.— 
Place in a 750 cc. round-bottomed flask, provided with a return 
condenser, 60 grams of finely powdered anhydrous sodium ace- 
tate (see experiment 66a), and add through the condenser, very 
slowly, 70 grams (88 cc.) of concentrated sulphuric acid Add, 
next, 65 grams of isoamyl alcohol. Heat on a wire gauze for one- 
half hour. Connect the flask with a condenser arranged for 
distillation, and distil as long as liquid passes over. Pour the 
distillate into a separatory funnel, and wash it twice with an equal 
volume of water. Separate the ester, and dry it over anhydrous 
calcium chloride. Pour off the liquid and distil. Collect and 
weigh the portion which boils at 137°-141°. Calculate the theo- 
retical yield from the sodium acetate used, and the percentage 
of this obtained. Test the solubility of isoamyl acetate in con- 
centrated sulphuric acid. 

Isoamyl acetate boils at 139°. The yield should be about 
67 grams. | 


Nortr.—It is often advisable to prepare esters from salts rather than from 
the free acids. The salts can be more readily obtained in an anhydrous con- 
dition and, being solids, smaller quantities can be handled conveniently. In 
the preparation of esters from salts, enough sulphuric acid must be added 
to liberate the organic acid; equal molecular quantities must be used, 
since acid sulphates are formed. A small excess of sulphuric acid should be 
present to act as a catalytic agent. Enough of the alcohol is used to interact 
with both the organic acid and the excess of sulphuric acid. 


Fats AND OILS 


105. Properties of Fats and Oils (Smctions 135-137).—(a) 
Solubility of fats and oils —Test the solubility of 1 gram of lard 
and 1 cc. of olive oil in water, ether, alcohol, chloroform, and 
petroleum ether. 

(b) Extraction of fat.—Partly fill a small evaporating dish with 
sand; pour 25 cc. of milk into the dish and evaporate on the steam- 
bath to dryness. Grind the residue and put it, together with 
100 cc. of ether or petroleum ether, into a dry stoppered bottle. 


Eo OO ee 


ETHERS, ESTERS, AND ANHYDRIDES 79 


At the next exercise filter off the ether into a beaker, and set 
it aside to evaporate spontaneously. Examine the resulting 
product. What is it? 

(c) Saponification of a fat—Read your notes on the saponi- 
fication of lard (experiment 92a, page 64). If you have not 
performed the experiment, do so now. | 

(d) Saponification of olive oil—Warm together on the steam- 
bath for 10 minutes 5 cc. of olive oil and 1 gram of sodium hy- 
droxide dissolved in 20 cc. of alcohol. Pour the product into 
water and add dilute sulphuric acid. (Kq.) 

(e) Sapontfication of butter—Saponify 15 grams of butter 
with 5 cc. of a concentrated solution of sodium hydroxide (1:1), 
carrying out the experiment as described in the similar experi- 
ment with lard (experiment 92a, page 64). As soon as the mix- 
ture is thick and homogeneous, pour it into 15 cc. of water. Trans- 
fer the solution of soap to a distilling flask, acidify with 25 ce. 
of sulphuric acid (1 part of acid to 4 of water), and distil 
over about 15 cc. Test the distillate with litmus paper. Are 
the volatile acids soluble in water? Note the odor of the solu- 
tion. What causes the odor? Determine whether the oily 
layer in the distilling flask contains acids. Find out if it is solu- 
ble in alkalies. What happens when an acid is added to the alka- 
line solution so formed? 

(f) Test for unsaturated glycerides.—Dissolve 5 cc. of olive 
oil or cotton-seed oil in 5 cc. of carbon tetrachloride, and add a 
solution of bromine in carbon tetrachloride, drop by drop. 

(g) Owls and concentrated sulphuric acid—Add to 10 ce. of 
olive oil or cotton-seed oil contained in a small beaker 5 cc. of 
concentrated sulphuric acid. Stir with a thermometer and note 
the rise in temperature. Repeat, using kerosene. Is there a 
difference? Explain. 

(h) Emulsification of oils——In five test-tubes prepare the fol- 
lowing mixtures: (1) 10 cc. of a 0.2 per cent solution of sodium 
carbonate and 2 drops of neutral olive oil. (2) 10 ce. of a 0.2 
per cent solution of sodium carbonate and 2 drops of rancid olive 
oil. (3) 10 cc. of a warm solution of soap and 2 drops of the 
neutral oil. (4) 10 cc. of white of egg solution and 2 drops of 
neutral oil. (5) 10 cc. of water and 2dropsof neutral oil. Shake 
the tubes very vigorously and let them stand for a few minutes. 


80 EXPERIMENTAL ORGANIC CHEMISTRY 


Record the results in each case. Under what conditions is the 
oil most perfectly emulsified? 
Examine a drop of milk under a microscope. 


Notrs.—(b) The fat can be extracted from milk in the usual way in a 
separatory funnel with ether. In the analysis of foods, however, the prod- 
uct is always dried before extraction. Milk can be dried as directed above, 
or it can be absorbed on filter-paper which is then dried. 

(d) If saponification is complete there should be no separation of oil 
when the product is diluted with water. 

(e) When this reaction is carried out quantitatively and 5 grams of fat 
or oil are used, the number of cubic centimeters of a tenth normal solution of 
sodium hydroxide required to neutralize the soluble volatile acids is called the 
Reichert-Meissl number. 

(g) The reaction illustrated in this test is the basis of a method used in 
the analysis of oils. The number of degrees rise in temperature when 50 
grams of an oil are treated with 10 cc. of sulphuric acid, in a vessel con- 
structed in such a way as to avoid loss of heat by radiation, is called the 
Maumené number of the oil. 

(h) Oils which have become rancid contain free fatty acids. The latter 
can be detected as follows: Dissolve in about 2 cc. of alcohol a drop 
of phenolphthalein solution and 1 or 2 drops of a very dilute solution of 
sodium hydroxide. To the resulting solution, which should have a light 
pink color, add an alcoholic solution of the fat to be tested for free acid. 
If the latter is present the color will disappear. . 

If a sample of rancid olive oil is not available for the experiment, mix 
together the neutral oil and oleic acid in the proportion of 1 ec. of the former 
to 1 drop of the latter, and shake 2 drops of the mixture with the solution 
of sodium carbonate. 

The factors which lead to the formation of emulsions are not definitely 
known. The most permanent emulsions are formed when an insoluble 
oil is shaken with a solution which contains a substance that interacts with 
one of the constituents of the oil to produce a colloid. This occurs when an 
oil containing free fatty acids is shaken with an aqueous solution of an 
alkali. A layer of soap is formed around the particles of the oil, and it is 
probable that a layer of oil may surround the colloidal particles of soap. 
When a solution of egg albumin is shaken with olive oil, a layer of the coagu- 
lated protein is formed around the drops of the oil and emulsification 
takes place. 


CHAPTER VII 
ALDEHYDES AND KETONES 


106. Formation and Properties of Formaldehyde (Srctions 
142, 143).—(a) Prepare a dilute solution of formaldehyde by 
oxidizing methyl alcohol as directed in experiment 776, page 53, 
and make the following tests: 

(6) Perform experiment 77b. Repeat the experiment, using 
6 drops of a cold saturated alcoholic solution of gallic acid in place 
of the solution of resorcin. 

(c) Formaldehyde in milk.n—Mix 2 ec. of the formaldehyde 
solution prepared in (a) above with 5 cc. of milk, add 3 drops 
of a solution of ferric chloride, hold the tube in a slanting posi- 
tion, and pour down it slowly 5 ce. of concentrated sulphuric 
acid in such a way that the acid forms a layer at the bottom of the 
tube. Repeat the test with a sample of milk free from formalde- 
hyde, which has been diluted with an equal volume of water. 

(d) Reducing action of formaldehyde.—Clean a test-tube thor- 
oughly by boiling a strong solution of sodium hydroxide in it, 
and then washing with water. Place in the test-tube about 5 cc. 
of a dilute solution of silver nitrate, and add a dilute solution of 
ammonia, drop by drop, until the precipitate first formed is just 
dissolved. Add about 1 cc. of the dilute solution of formalde- 
hyde and put the tube into warm water. 

(e) Formaldehyde and Schiff’s reagent—Add a few drops of 
the solution of formaldehyde to 5 cc. of Schiff’s reagent. 

(f) Formaldehyde and Fehling’s solution—Add 1 cc. of the’ 
dilute solution of the aldehyde to 5 cc. of Fehling’s solution and 
heat to boiling. The preparation of Fehling’s solution is de- 
scribed in the Appendix. (See note below and Srction 151.) 

(g) Polymerization of formaldehyde.—Evaporate on the steam- 
bath 10 ce. of formalin (a 40 per cent solution of formaldehyde). 
Heat some of the residue over a free flame and note cautiously 
the odor. 

6 81 


82 EXPERIMENTAL ORGANIC CHEMISTRY 


(h) Formaldehyde and proteins.—Place in a solution of 1 cc. 
of formalin and 5 cc. of water a thin piece of gelatin and let it 
stand for from 10 to 20 minutes. Place the gelatin in water 
and heat to boiling. Try the action of boiling water on gelatin 
which has not been in contact with formalin. 

Notrs.—(b) In these tests very dilute solutions of formaldehyde should 
be used, since strong solutions give precipitates which obscure the colors 
that develop. 

(c) A test similar to that aera: is made by pouring into the tube con- 
taining the milk, so that two layers are formed, concentrated hydrochloric 
acid containing a small amount of ferric chloride. - . 

(e) It should be noted that alkalies or salts which give an alkaline reac- 
tion produce a pink color with Schiff’s reagent; it also becomes colored when 
heated. The preparation of the reagent is described in the appendix. 

(f) Fehling’s solution is much used in testing for aldehydes. I+ consists 
of a solution prepared by dissolving copper sulphate, sodium hydroxide, and 
sodium potassium tartrate in water, the tartrate serving to keep in solution 
the copper hydroxide, which would otherwise precipitate. The aldehyde 
reduces the cupric compound in the alkaline solution to cuprous oxide. 


107. Preparation of Acetaldehyde from Alcohol (SrcTion 
144).—A 500 cc. distilling flask containing 80 grams of powdered 
potassium or sodium bichromate is closed by a cork bearing a 
separatory funnel, and connected with a long condenser through 
which a rapid stream of cold water passes. The condenser is 
attached by means of an adapter to areceiver which is surrounded 
by ice-water. Drop in slowly through the funnel a cold mixture 
of 160 cc. of water, 40 grams of alcohol, and 70 cc. of concentrated 
sulphuric acid. A vigorous reaction takes place; as this subsides 
the mixture isrun in more rapidly. ‘The flask is shaken occasion- 
ally to prevent the bichromate from forming a cake at the bottom. 
When all the mixture has been added, and the action has ceased, 
replace the funnel by a thermometer and heat the flask very 
gently; remove the flame as soon as reaction sets up again. Re- 
peat the heating in this way until reaction ceases when the flame 
is withdrawn. Care should be taken to prevent the rise of the 
thermometer beyond 65°. Place the distillate in a small distilling 
flask provided with a long condenser and receiver cooled by ice- 
water, and distil very slowly collecting the portion which boils 
between 20° and 35°. Acetaldehyde boils at 21°. The product 
obtained contains some water, but can be used for the experi- 
ments described below. 


ALDEHYDES AND KETONES 83 


108. Properties of Acetaldehyde (Srncrions 144-147) — 
(a) Aldehyde and sodium hydrogen sulphite-—Shake 2 cc. of the 
aldehyde prepared in the experiment just described with 5 ce. 
of a saturated solution of sodium hydrogen sulphite. (£q.) 
Note the disappearance of the odor of aldehyde. Add 5 ce. of 
a strong solution of sodium carbonate and heat, noting the odor. 
(Eq.) 

(b) Aldehyde and bromine.—To 2 cc. of the aldehyde add 
bromine, drop by drop, as long as the solution is decolorized. 
The bromine should be added slowly as the reaction at first is 
delayed. When the reaction is complete add about 10 cc. of 
water. Does a heavy oil separate? (Kq.) 

(c) Polymerization of aldehyde—Dip a glass rod into con- 
centrated sulphuric acid, and remove as much of the acid as 
possible by shaking. Dip the rod into 2 cc. of aldehyde. Note 
the reaction. (Hq.) Add 5 cc. of water. 

(d) Aldehyde resin.—Boil a few drops of aldehyde in 5 ce. of 
water with a few drops of a solution of sodium hydroxide. Note 
the appearance and odor of the product. Repeat the test using 


_a solution of formaldehyde. 


(e) Oxidation of aldehyde—Add, in small portions, a dilute 


‘solution of potassium permanganate to a solution of 2 cc. of 


aldehyde in 5 cc. of water. (Kq.) Recall the action of an un- 
saturated hydrocarbon with a solution of potassium perman- 
ganate. Is the test with this salt a positive proof that a com- 
pound contains a double or triple bond between carbon atoms? 
How could you distinguish between a solution of an aldehyde and 
one of ethylene? 

(f) Reducing action of aldehyde—Warm 5 ceo bs of aldehyde 
with 5 ce. of Fehling’s solution. 

(g) Tollen’s reagent for aldehydes——Test 3 drops of aldehyde 


with an ammoniacal solution of silver nitrate as described in 


experiment 106d, page 81, or without heating with Tollen’s 
reagent.! (Hq.) Clean the test-tube to be used by boiling it 
out with a solution of sodium hydroxide. 

(h) Schiff’s reagent and aldehydes.—Test a few drops of the 
aldehyde with about 5 cc. of Schiff’s reagent.! 


1 See Appendix. 


84 EXPERIMENTAL ORGANIC CHEMISTRY 


109. Formation of Acetaldehyde from an Acetate (SrctTIon 
144) —Mix together 5 grams of sodium formate and 6 grams of 
anhydrous sodium acetate in an 8-inch test-tube. Place the tube 
in an inclined position and attach by means of a cork a delivery- 
tube which dips under water contained in a test-tube. Heat for 
a few minutes. Test the resulting solution of aldehyde with 
Schiff’s reagent. 


KETONES 


110. Formation of Acetone from an Acetate (Section 155).— 
Place in an 8-inch test-tube 7 grams of calcium acetate and 7 
grams of anhydrous sodium acetate which have been intimately: 
mixed by grinding together in a mortar. Clamp the tube in a 
horizontal position and connect it with a condenser. Tap the 
tube gently so that a channel is formed along its whole length. 
Heat until the acetates glow, turning the tube from time to 
time, so that all of the salts can be heated to a high temperature. 
Redistil the liquid and determine its boiling-point. 

Acetone boils at 56°. The yield is from 3 to 4 grams. 


Notr.—Sodium acetate is mixed with calcium acetate in this preparation 
in order to facilitate the formation of acetone. 


111. Properties of Acetone (Srcrions 155, 157, 158).—(a) 
Acetone and Schiff’s reagent.—Add a few drops of acetone to 5 ce. 
of Schiff’s reagent. Examine the solution after it has stood some 
time. 

(b) Acetone and sodium hydrogen sulphite——Mix 5 ce. of ace- 
tone with 5 cc. of a saturated solution of sodium hydrogen sul- 
phite; shake and cool. (Kq.) 

(c) Acetone and Tollen’s reagent.—Test a few drops of acetone 
dissolved in 5 cc. of water with an ammoniacal solution of silver 
nitrate or with Tollen’s reagent. 

(d) Conversion of acetone into iodoform.—Apply the iodoform 
test to a dilute solution of acetone. (See experiment 810, 
page 57.) 

(e) Acetone and phosphorus pentachloride-—Hoov.—To 5 ce. 
of acetone contained in a test-tube placed in cold water add, with 
constant shaking, small quantities of phosphorus pentachloride 
as long as any reaction takes place. Pour the contents of the 


ALDEHYDES AND KETONES 85 


tube slowly into cold water. Does a heavy liquid separate? 
(Eq.) 

(f) Identification of acetone-—Acetone can be converted into 
a solid compound which is valuable in its identification, especially 
if the ketone is in a dilute aqueous solution. The substance 
prepared is formed as the result of the interaction of acetone and 
benzaldehyde, CsH;s.CHO, in the presence of an alkali; it is 
called dibenzalacetone. The reaction is as follows: 

2C6eHs.CHO + (CHs)2CO = (CeHs.CH:CH).2CO + 2H2O 

Place in a small flask 1 cc. of acetone, 4 ce. of water, 4 cc. of 
benzaldehyde, 20 cc. of alcohol, and 5 ce. of a 10 per cent solution 
of sodium hydroxide. Boil gently for 5 minutes. Cool and 
shake. Filter off the crystals and wash them with 20 ce. of cold 
alcohol. Recrystallize from 20 cc. of boiling alcohol. Let the 
solution cool. Filter and wash with 10 ce. of cold alcohol. Dry 
on a porous plate and determine the melting-point of the crystals. 
Dibenzalacetone crystallizes in yellow plates and melts at 
111°-112°. 


CHAPTER VIII 
AMINES AND AMIDES 


112. Preparation of Methylamine from Acetamide (SrcTion 
162).—Place into a 1 liter flask 100 cc. of water and 36 grams of 
fresh bleaching powder. Add 10 grams of acetamide dissolved 
in 25 cc. of water in small portions and shake. Add slowly a 
cold solution of 25 grams of sodium hydroxide in 100 cc. of water. 
Arrange the apparatus to distil with steam (see Fig. 12, page 19), 
and connect an adapter by means of a tightly fitting rubber 
stopper with the end of the condenser. Place the end of the 
adapter just below the surface of 50 cc. of cold water contained 
in a beaker, and distil with steam. From time to time remove 
the adapter, and test the distillate with litmus paper. Stop the 
distillation when methylamine ceases to distil over. The yield 
in this preparation, calculated from the methylammonium chlor- 
ide obtained (see experiment 113d below), should be 70 per cent 
of the theoretical. 


Norr.—In the preparation of methylamine by Hofmann’s reaction, 
bromine and potassium hydroxide are commonly used. The use of bleaching 
powder, instead of these reagents, which form potassium hypobromite, 
avoids the handling of large quantities of bromine, and reduces the cost of 
the preparation. The amount of bleaching powder to be used is determined 
by the percentage of available chlorine which it contains. The proportions 
given above are based on a bleaching powder which contains about 35 per 
cent of available chlorine. 


113. Properties of Methylamine (Sections 163, 164).—(a) 
Basic properties of a solution of methylamine——Test the dis- 
tillate obtained in the experiment just described with pink litmus 
paper. 

(b) Methylamine and solutions of metallic salts. Add a little 
of the distillate, drop by drop, as long as any change occurs, to 
1 cc. of a dilute solution of copper sulphate. Repeat with asolu- 
tion of ferric chloride. Add ammonia to solutions of these salts. 

86 


ee 


AMINES AND AMIDES 87 


Write equations for the reactions in the case of ammonia and of 
methylamine; the reactions in the two cases are analogous. 

(c) Carbylamine reaction—Hoov.—Warm 1 ce. of the dis- 
tillate with 2 drops of chloroform and 2 cc. of an alcoholic solu- 
tion of potassium hydroxide, which may be prepared by heating 
a little of the solid compound with alcohol and decanting off the 
solution. (Hq.) Note the odor produced. Acidify the con- 
tents of the tube before pouring into the sink. 

(d) Methylammonium chloride—Make the rest of the distil- 
late slightly acidic with hydrochloric acid, and evaporate the 
solution to dryness on the steam bath. Dissolve the salt in the 
smallest possible amount of boiling absolute alcohol; a small 
amount of ammonium chloride may be left as an insoluble residue. 
To dissolve the salt, add to the beaker on a steam-bath about 
25 cc. of the alcohol; cover with a watch-glass, and let the salt 
digest with the hot alcohol for a few minutes. Filter through 
a funnel from which the stem has been cut (see Fig. 1, page 6). 
Continue the addition and digestion as long as the solvent ap- 
pears to dissolve the salt. About 100 cc. of alcohol will be re- 
quired.. Cool the combined filtrates, and add an equal volume 
of ether. Filter off the crystals by suction and dry them on a 
porous plate. Determine the weight and the melting-point of the 
methylammonium chloride obtained. 

(e) Methylammonium chloride and alkalies—Heat together in 
a test-tube a very small amount of the salt with 2 cc. of a solu- 
tion of sodium hydroxide. (Hq.) Note the odor of the gas. 

(f) Inflammability of methylamine—Place about 0.5 gram 
of methylammonium chloride and an equal amount of lime 
in a dry test-tube, and heat. Apply a flame to the gas. Does 
it burn? Repeat with ammonium chloride. Does ammonia 
burn in air? 

(g) Methylammonium chlorplatinate-—Dissolve a small amount 
of methylammonium chloride in a few drops of alcohol, and add, 
drop by drop, a 10 per cent solution of platinic chloride. Re- 
peat, using a few drops of a strong aqueous solution of am- 
monium chloride. The reactions in the two cases are analogous. 
Write the equations for both reactions. 

(h) Decomposition of methylammonium nitrite—Mix in a test- 
tube about 0.5 gram of methylammonium chloride with twice 


88 EXPERIMENTAL ORGANIC CHEMISTRY 


its weight of sodium nitrite and about 5 cc. of water. Connect 
the tube by means of a cork with a delivery-tube arranged to 
collect a gas over water. Heat the solution gently and collect 
two test-tubes full of the gas. (Hq.) Test the second tube for 
nitrogen with a glowing splinter. JDistil over about 3 cc. from 
the tube into a second tube, surrounded by cold water. Test 
the distillate for methyl alcohol (experiment 776, page 53). 


114. Isolation of Lecithin from Egg-yolk (Srmcrion 174).— 
Grind the yolk of one hard-boiled egg with 50 ce. of ether. Filter 
and wash the solid residue twice with 10 cc. of ether. Evaporate 
off the ether on the steam-bath, or distil it off from a small 
flask. Extract the residue twice with hot alcohol, using 10 ce. 
each time. Pour off the alcohol from the heavy oil through a 
small filter. Evaporate off the alcohol, dissolve the residue in 
10 ce. of cold ether, and add 10 ec. of acetone. Stir until the 
particles of the precipitated lecithin adhere together and form 
a ball. Place the latter on a filter-paper. Describe its proper- 
ties. Boil about one-fourth of the lecithin with about 10 ce. 
of a 10 per cent solution of sodium hydroxide. Note the odor 
of the gas evolved. What is it? Cool the solution. Is there 
any evidence of the formation of a soap? Filter, dissolve the 
precipitate in warm water and add dilute hydrochloric acid to 
the solution. What is precipitated? Test a part of the lecithin 
for nitrogen and for phosphorus ($$58 59, 61, page 39). 


Notr.—Ether dissolves from egg-yolk, in addition to lecithin, some fat 
and protein. The protein and a part of the fat are removed by extracting 
the residue from ether with alcohol. The lecithin is finally separated by 
adding acetone to an ethereal solution of the lecithin and fat. The latter is 
soluble in acetone while the lecithin is insoluble. 


AMIDES 


115. Preparation of Acetamide from Ethyl Acetate (SmcTion 
178).—Mix in a 250 ce. distilling flask 50 grams of ethyl acetate 
and 100 cc. of a concentrated aqueous solution of ammonia 
(sp. gr. 0.90). Close the flask with corks and let the mixture 
stand, with occasional shaking, until the two layers first formed 
have disappeared. (Hq.) Arrange the flask for distillation with 
a thermometer and water condenser, and use as a receiver a 


AMINES AND AMIDES 89 


distilling flask or a filter-bottle, the side-arm of which is provided 
with a tube which dips under water; the latter precaution is taken 
to absorb the large quantity of ammonia which is given off in 
the distillation. Distil carefully; collect the first part (about 
10 cc.) of the distillate separately and test it for ethyl alcohol. 
When the thermometer registers 160°, replace the water-con- 
denser by an air-condenser, change the receiver, using this time 
a beaker, and collect what distils at 160°-225°. As the tempera- 
ture rises the acetamide solidifies in the condenser to a crystalline 
mass, which can be readily liquefied by warming the condenser 
cautiously with a free flame. When the distillate is cold pour 
off from the crystals in the receiver any liquid present, and dry 
the crystals on a porous plate. Weigh the product obtained 
and determine its melting-point. Calculate the percentage 
yield obtained. ‘The slightly impure acetamide may be purified 
by a second distillation, or by crystallizing it from a mixture 
of one volume of alcohol and two volumes of ether. If the 
product obtained in the first distillation does not melt sharply, 
recrystallize a small portion of it. | 
Acetamide melts at 82°, and boils at 222°. The yield obtained 
in the preparation should be about 65 per cent of the theoretical. 


Nore.—The odor of the amide prepared as directed above is due to an 
impurity which is present in small quantity. By a single recrystallization 
the compound is obtained in an odorless condition. 


116. Properties of Acetamide (Section 178).—(a) Hydrolysis 
of acetamide.—Mix about 0.5 gram of acetamide with about 5 ce. 
of a solution of sodium hydroxide, shake and observe whether 
the odor of ammonia is present. Heat the solution to boiling. 
Is ammonia set free? (Eq.) 

(6b) Heat to boiling for 1 minute about 0.5 gram of acetamide 
with 2 cc. of dilute sulphuric acid. Cool, and make alkaline with 
a solution of sodium hydroxide. Does the solution smell of am- 
monia? Explain. 

(c) Mercury salt of acetamide—Add an excess of a solution 
of sodium hydroxide to 2 cc. of a solution of mercuric chloride. 
(Eq.) Determine whether the precipitate dissolves when a little 
acetamide is added. (Hgq.) Test the solution for mercury with 
hydrogen sulphide. 


90 EXPERIMENTAL ORGANIC CHEMISTRY 


(d) Acetamide and nitrous acid—To an aqueous solution of 
acetamide add a few crystals of sodium nitrite and a few drops 
of dilute sulphuric acid. (qs.) 


117. Preparation of Urea from a Cyanate (Section 180).— 
Dissolve 8 grams of potassium cyanate in 20 cc. of hot water 
and 13 grams of ammonium sulphate in 20 cc. of hot water. Mix 
the solutions and evaporate to dryness on the steam-bath. 
(Eq.) Grind the product to a fine powder and dry on the steam- 
bath for 15 minutes. Place the solid in a dry beaker and add 
25 ce. of alcohol. Cover with a watch-glass, and let the mixture 
digest just below the boiling-point of alcohol for a few minutes. 
Decant off the liquid through a filter and digest a second time. 
If the solution is colored, boil the combined filtrates with a little 
bone-black. Filter and evaporate on the steam-bath to crystal- 
lization (see §9, page 6). When the solution is cold, filter off 
the crystals by suction (see §12, page 7) and dry them on a 
porous plate. From the filtrate a second crop of crystals may 
be gotten by evaporation and the addition of an equal column 


of ether to the cold solution. Weigh the urea obtained and de-. 


termine its melting-point. 

Urea melts at 132°, and can be crystallized from hot amyl 
alcohol. 

Norse.—The blue substance formed at times in this preparation is probably 
produced as the result of the following cause: Commercial potassium cya- 
nate may contain potassium ferrocyanide. If this is the case, when a solu- 
tion of the salt is evaporated in the air with ammonium sulphate containing 
a trace of iron, Prussian blue is formed. 

118. Properties of Urea (Sections 180, 181).—(a) Nitrate of 
urea.—Dissolve a crystal of urea in a drop of water on a micro- 


scope slide; place near this solution a drop of concentrated 


nitric acid, and bring the two together by touching with a glass 
rod. (H#q.) Examine the crystals under the microscope. 

(b) Urea and oxalic acid.—Repeat (a) above but use a satu- 
rated solution of oxalic acid in place of nitric acid. (q.) 

(c) Hydrolysis of urea.—Treat about 0.5 gram of urea with 
5 cc. of a solution of sodium hydroxide. Note whether ammonia 
is given off. Explain. Boil the solution for a minute or two 
and observe if ammonia is given off freely. (Hq.) Test the 
vapor with litmus paper. 


ee eee 


AMINES AND AMIDES 91 


(d) Urea and nitrous acid.—Place in a test-tube 0.1 gram of 
sodium nitrite and 10 cc. of water; in another tube put 0.1 gram 
sodium nitrite, 10 cc. of water and 0.2 gram of urea. Add to 
_ each tube 1 cc. of dilute acetic acid. Compare the amount and 
color of the gas given off in each case. (K qs.) 

(e) Urea and sodium hypobromite-—Prepare an alkaline solu- 
tion of sodium hypobromite by adding 3 drops of bromine to 
5 cc. of a dilute solution (10 per cent) of sodium hydroxide. Add 
this solution to a dilute solution of urea. (Kq@.) 

(f) Urea and mercuric nitrate—To a dilute solution of urea 
add a 1 per cent solution of mercuric nitrate. A compound of 
the formula CO(N H2)2.Hg(NO3)2.HgO is precipitated. 

(g) Action of heat on urea: biuret (Section 181).—Heat cau- 
tiously about 0.5 gram of urea in a dry test-tube; continue the 
heating until a white opaque solid is formed. The residue is a 
mixture of biuret and cyanuric acid (Section 201). Treat the 
residue when cold with about 5 cc. of water, shake, pour off 
the aqueous solution of biuret, and add 5 cc. of a solution of 
sodium hydroxide and a few drops of a dilute (1 per cent) solu- 
tion of copper sulphate. 

Dissolve the residue insoluble in water in a little ammonia, 
add a few cubic centimeters of a solution of barium chloride and 
shake. A precipitate of barium cyanurate is formed. 


Notrs.—(a) The nitrate of urea is difficultly soluble in cold water and in 
nitric acid. This fact is made use of in the isolation of urea from urine. 

(c) Ammonium salts can be distinguished from amides by means of sodium 
hydroxide; the former yield ammonia in the cold: 

(ec) Ammonium salts give nitrogen when treated with a solution of 
sodium hypobromite; they must, therefore, be absent when applying the 
test to urea. This reaction is used in the clinical examination of urine for 
urea. 

(f) Many substances related to acid amides, for example the proteins, 
give precipitates with solutions of mercuric salts. 

(g) This test for biuret is not characteristic; it is given by many substances 
in which there is a linking of atoms similar to that in biuret. The test is 
useful in the study of proteins. 


CHAPTER IX 
CYANOGEN AND RELATED COMPOUNDS 


119. Formation of Cyanogen (Section 188).—(a) From mer- 
curtc cyanide.—CavuTION.—Cyanogen is a poisonous gas. Per- 
form the experiment under a hood. Heat in a small dry test-tube — 
over a free flame about 0.5 gram of mercuric cyanide. Ignite 
the gas generated. Note the unusual color of the different parts 
of the flame. (q.) 

(b) From copper sulphate and potassium cyanide.—CavuTIoONn.— 
Potassium cyanide is very poisonous. It should not be touched 
with the fingers; use a spatula or handle small pieces with pin- 
cers. Hoop.—Add to 5 ce. of a cold saturated solution of copper 
sulphate a cold saturated solution of potassium cyanide until the 
precipitate first formed dissolves. (Hq.) Heat to boiling (#q.) 
and ignite the gas evolved. Add a solution of potassium iodide 
to a solution of copper sulphate. (Hq.) Determine by an 
appropriate test if iodine is liberated. 


120. Formation of Potassium Cyanide from Potassium Ferro- 
cyanide (Section 193).—Heat to a high temperature in a porce- 
lain crucible about 1 gram of potassium ferrocyanide. (Kq.) 
When cold add water, and heat to boiling. Pour off the solution 
and test for a cyanide according to the next experiment. 


121. Test for a Soluble Cyanide (Suction 194).—To 1 ce. of 
a dilute solution of potassium cyanide add 5 drops of a solution of 
sodium hydroxide and 5 drops of a solution of ferrous sulphate; 
heat to boiling, cool, and add dilute hydrochloric acid, drop by 
drop, until the solution just shows an acid reaction. If no color 
develops add 3 drops of a solution of ferric chloride. Potassium 
ferrocyanide is formed from the potassium cyanide and ferrous 
sulphate; the ferrocyanide and the ferric salt then form Prussian 
blue. (EKgqs.) 

Notr.—It is usually not necessary to add ferric chloride, since the 


ferrous sulphate contains enough ferric salt to give the reaction. An 
92 


CYANOGEN AND RELATED COMPOUNDS 93 


excess of hydrochloric acid should be avoided since it interferes with the 
formation of the ferric ferrocyanide. 


122. Action of Cyanides on the Soluble Salts of Heavy Metals 
(Section 193).—(a) Add a few drops of a solution of potassium 
cyanide to a solution of ferric chloride. (Kq.) Next add an 
excess of potassium cyanide (Hq.), acidify, and then add a solu- 
tion of ferrous sulphate. (£q.) 

(b) Add a few drops of a solution of potassium cyanide to a 
solution of silver nitrate (Hq.); add an excess of the cyanide. 
(Hq.) Determine if silver chloride is soluble in potassium cya- 
nide. Precipitate some silver cyanide and determine its solu- 
bility in nitric acid and in ammonia. How could you distinguish 
silver chloride from silver cyanide? 


123. Properties of Potassium Ferrocyanide (Srcrion 194).— 
(a) Conversion into hydroferrocyanic acid.—Add concentrated hy- 
drochloric acid to about 10 cc. of a saturated solution of potas- 
sium ferrocyanide as long as a precipitate is formed. (q.) 
Pour off the liquid and place a part of the crystals on a porous 
plate. They turn blue due to oxidation. 

(b) Decomposition with strong sulphuric acid.—In a test-tube 
moisten with 5 drops of water about 1 gram of powdered potas- 
sium ferrocyanide and add 5 ce. of concentrated sulphuric acid. 
Heat and apply a flame to the gas evolved. (£q@.) 

(c) Ferrocyanides of heavy metals—Add a solution of potas- 
sium ferrocyanide to solutions of salts of ferric iron, silver, copper, 
and mercury. (Kgqs.) 


124. Preparation of Potassium Ferricyanide from Potassium 
Ferrocyanide (Smction 195).—Dissolve 5 grams of potassium 
ferrocyanide in about 20 cc. of warm water, cool and add bromine 
in slight excess, drop by drop, with constant shaking. (£q.) 
Evaporate to crystallization under the hood, and set aside the 
solution to crystallize. 


125. Properties of Potassium Ferricyanide (Smction 195).— 
(a) Ferricyanides of heavy metals.—Add a solution of potassium 
ferricyanide to solutions of salts of ferric iron, ferrous iron, silver, 
copper, and mercury (£q.) 

(b) Potassium ferricyanide as an oxidizing agent.—In a small 


94 EXPERIMENTAL ORGANIC CHEMISTRY 


beaker dissolve 2 grams of lead nitrate in about 10 cc. of boiling 
water, and add a solution of sodium hydroxide until the precipi- 
tate first formed has dissolved. Next add a strong aqueous solu- 
tion of 4 grams of potassium ferricyanide, and heat to boiling. 
(Eq.) Filter off the precipitate, test the filtrate for a ferrocyanide 
and determine if the precipitate is lead dioxide, PbOs. Add 
hydrochloric acid to a little of the substance and heat. (Kq.) 
Norr.—(b) An alkaline solution of potassium ferricyanide is a valuable 
mild oxidizing agent, which is frequently used in the oxidation of organic 


compounds. The oxidizing power is equivalent to that represented in the 
following equation: 


2K3;Fe(CN)¢ + 2KOH = 2K4Fe(CN)s + HO +0 


ALKYL CYANIDES 


126. Preparation of Methyl Cyanide (Smcrion 197).—Weigh 
directly into a dry 100 ce. distilling flask 20 grams of phosphorus 
pentoxide and add 20 grams of powdered acetamide; stir the 
mixture and shake it. Close the flask with a cork bearing a 
thermometer, connect with a condenser, and use a 25 cc. dis- 
tilling flask as a receiver. Heat cautiously with a small flame, 
kept constantly in motion, as long as any liquid distils. Add to 
the distillate about 2 grams of phosphorus pentoxide, and re- 
distil, collecting the portion which boils at 80°-82°. Weigh the 
distillate and calculate the percentage yield obtained. 

Methyl cyanide (acetonitrile) boils at 81.6°. The yield ob- 
tained in the above experiment should be 50-60 per cent of the 
theoretical. 


127. Hydrolysis of Methyl Cyanide (Section 197).—(a) 
Heat about 1 cc. of methyl cyanide with a dilute solution of 
sodium hydroxide, and note the odor of the gas evolved. (£q.) 

(b) In a small round-bottomed flask mix 3 ec. of water and 6 
cc. of concentrated sulphuric acid; cool the mixture and add 5 
grams of methyl cyanide. Connect the flask with a return con- 
denser and boil gently for 15 minutes. (Kq.) Dilute with about 
5 ce. of water and distil off about 5 cc. Test the distillate for 
acetic acid. (See experiment 91, page 64.) Make a part of the 
contents of the flask strongly alkaline with sodium hydroxide 
and note the odor. 


ee ee ee eae RT, ee ee ee ee eee ae ee ae 





CYANOGEN AND RELATED COMPOUNDS 95 


128. Formation of an Isocyanide (Section 198).—Repeat the 
carbylamine test for primary amines (experiment 113c, page 87), 
in which an isocyanide is formed, or apply the test to aniline, 
CsH;sNH2, which is a primary amine containing the phenyl 
radical, CsH;; phenyl isocyanide, CsH;NC, is formed. Proceed 
as follows: Hoop.—Warm together 2 drops of aniline, 3 drops of 
chloroform, and 2 ce. of an alcoholic solution of potassium hy- 
droxide. (Hq.) Caution.—As phenyl isocyanide has a very 
disagreeable odor and is poisonous, the tube containing it should 
be washed thoroughly under the hood. 


CHAPTER X 
HALOGEN COMPOUNDS 


129. Preparation of Methyl Iodide from Methyl Alcohol 
and Phosphorus Iodide (Srcrions 49, 204).—In a 200 cc. round- 
bottomed flask place 15 grams of methyl] alcohol and 3.2 grams of 
red phosphorus. Have ready a reflux condenser with cork at- 
tached. Place the flask in cold water and add in small portions 
at a time 38 grams of iodine; the addition should take about 
10 minutes. If the contents of the flask begin to boil, attach 
it to the reflux condenser; when reaction ceases add more iodine. 
Finally attach the flask to the condenser and let it stand for 
at least 4 hours (preferably over night). Distil through a con- 
denser from a water-bath, as long as any liquid passes over. 
The receiver should be placed in cold water as methyl iodide is 
very volatile. Wash the distillate by decantation with a dilute 
aqueous solution of sodium hydroxide until the lower layer is 
colorless, and then once with water. Separate the methyl 
iodide carefully from the water using a separatory funnel, and 
transfer it to a small distilling flask. Add about 10 grams of 
anhydrous calcium chloride. Stopper the flask, place a cork 
over the end of the side-arm, and set aside until the liquid is 
quite clear. Place a thermometer in the flask, connect the latter 
with a condenser, and distil from a water-bath. Note the boiling- 
point and weight of the methyl iodide. Calculate the theoretical 
yield from the iodine used (why iodine?), and the percentage of 
this obtained. 

Methyl iodide boils at 44°, and has the specific gravity 2.27 
at 15°. The yield in the experiment should be about 80 per cent 
of the theory. 


Notr.—An excess of the alcohol is usually taken in preparing alkyl halides 
by the method illustrated above. ‘The phosphorus and iodine are used in 
the proportions necessary to form phosphorus tri-iodide, PI;. The chief 
reaction which takes place is represented by the following equation: 


3CH;0H + P+ 3I = 3CH;I + P(OH); 
96 


HALOGEN COMPOUNDS 97 


The hydriodic acid which is evolved is produced as the result of side-reac- 
tions, which are described in the case of phosphorus trichloride in Section 
57, small print. 


130. Properties of Methyl Iodide (Srcrion 205).—(a) Action 
of light on methyl iodide.—Place in each of two small test-tubes 
2 cc. of methyl iodide and close the tubes tightly with corks. 
Put one tube in the desk in the dark, and allow the other to stand 
in direct sunlight. At the end of an hour or two, examine the 
two tubes. To remove the iodine set free, add a drop of mercury 
or some copper wire and shake. The alkyl iodides should be 
kept in well-stoppered bottles of brown glass. 

(b) Methyl rodide and silver nitrate—To a few drops of color- 
less methyl iodide suspended in water add a solution of silver 
nitrate and shake. Repeat, using a solution of methyl] iodide in 
alcohol and of silver nitrate in alcohol. (Kq.) 

(c) Methyl iodide and sodium hydroxide.-—Shake occasionally 
during half an hour a mixture of 1 cc. methyl iodide and 5 ce. 
of a dilute solution of sodium hydroxide. At the end of this 
time neutralize with dilute nitric acid, filter, and test a part of 
the filtrate for methyl alcohol according to experiment 77), 
page 53, and a part for an iodide. For other reactions of alkyl 
halides, see the experiments with ethyl bromide below. 


Notr.—(a,b, and c) Methyl iodide is much more reactive than the other 
alkyl iodides. Reactions analogous to those illustrated in the above experi- 
ments take place with the higher iodides, but much more slowly. The 
bromides are less reactive than the iodides; the chlorides are, in most cases, 
very stable. Tertiary halides are much more reactive than the halides 
derived from secondary and primary alcohols. 


131. Preparation of Ethyl Bromine from Alcohol, Potassium 
Bromide, and Sulphuric Acid (Srction 204).—Add to a mixture 
of 60 grams of alcohol and 50 cc. of water, contained in a 1 liter 
flask, 100 ce. of concentrated sulphuric acid. Cool thoroughly 
in running water, and add 100 grams of finely powdered potas- 
sium bromide. Connect the flask by means of a bent glass tube 
and a rubber stopper with a long condenser through which a rapid 
stream of water is passing, and fit an adapter by means of a cork 
to the end of the condenser. Use a 300 cc. Erlenmeyer flask as 
a receiver, and place it in a beaker about one-half full of cold 


water. Fill the receiver half full of water and adjust the con- 
7 


98 EXPERIMENTAL ORGANIC CHEMISTRY 


denser so that the end of the adapter is below the surface of the 
water. These precautions are taken because ethyl bromide is 
a very volatile liquid (boiling-point 39°). Place a sand-bath 
under the flask containing the reaction-mixture, heat with a 
large flame, and distil as rapidly as possible. As distillation 
proceeds, the ethyl bromide drops to the bottom of the receiver, 
and the aqueous part of the distillate finally overflows into the 


beaker. Distil until drops of the insoluble bromide cease to 


appear. About one hour is required for the distillation if it is 
carried on rapidly. 

Decant off most of the water from the ethyl bromide into a 
beaker, add a dilute solution of sodium hydroxide, shake, and 
decant. Wash again with water, and transfer to a separatory 
funnel; run off the lower layer into a small dry distilling flask, 
add anhydrous calcium chloride (about one-fourth the volume 
of the bromide), and close the flask tightly with corks. Set 
aside until the liquid is quite clear and no drops of water are 
visible; if the calcium chloride appears moist, add more and set 
aside again. Connect the flask with a long condenser and use 
as a receiver a dry flask surrounded by ice-water. Distil from 
a water-bath and collect the portion which boils at 35°-40°. 
Calculate the theoretical yield from the potassium bromide 
used (why from the bromide?) and the percentage yield obtained. 
Write equations for all reactions. Why does the solution turn 
red during the heating? (£q.) 

Ethyl bromide boils at 38.4° and has the specific gravity 1.47 
at 13°. The yield in this preparation should be about 80 per 
cent of the theoretical. 

Notr.—The ethyl bromide prepared in this way contains a small amount 
of ether, from which it cannot be separated readily by distillation, since ether 
boils at 35° and ethyl bromide at 38.4°. In separating the two substances 
advantage is taken of thefact that ether is solublein cold concentrated sul- 
phuric acid, while ethyl bromide is not soluble. The bromide prepared 
by the method given above can be purified by adding it slowly with con- 
stant shaking, to an equal volume of concentrated sulphuric acid kept cold 
by immersion in ice-water. After this treatment the liquids are separated 
and the ethyl bromide shaken with water, dried, and distilled. 


132. Properties of Ethyl Bromide (Srmcrions 205, 206).—(a) 
Solubilities of ethyl bromide.—Using about 1 cc. in each test, 
determine whether ethyl bromide dissolves in the following 


— = 


HALOGEN COMPOUNDS vo 


liquids: water, alcohol, ether, petroleum ether, and cold con- 
centrated sulphuric acid. 

(b) Test for bromine in ethyl bromide.—Test ethyl bromide for 
halogen with a copper wire ($60 page 40). 

(c) Ethyl bromide and silver nitrate—Shake about 2 cc. of 
ethyl bromide with 5 cc. of water to remove any free hydro- 
bromic acid which may be present. Separate the bromide by 
* means of a pipette and dissolve it in 5 ce. of an alcoholic solution 
of silver nitrate. Is silver bromide precipitated? Stopper the 
test-tube, and allow it to stand until the next laboratory exercise. 
Is silver bromide precipitated? Compare the result with that 
obtained with methyl iodide. 

(d) Ethyl bromide and alcoholic potassium hydroxide.—Shake 
a small piece of potassium hydroxide with 10 cc. of absolute 
alcohol. Filter off the liquid and dissolve in it 2 cc. of ethyl 
bromide. Boil for 1 minute. (Kq.) Dilute with water, acidify 
with a dilute solution of pure nitric acid, and add a solution of 
silver nitrate. 

(e) Ethyl bromide and magnesium.—Just cover the bottom 
of:a test-tube with magnesium powder. Add 2 cc. of ethyl 
bromide, 2 cc. of ether, and a very small piece of iodine; place 
the tube in warm water for 1 minute. Cool and add a little 
water. (Hq.) 

(f) Ethyl bromide and sodium.—To 5 cc. of ethyl bromide in 
a dry test-tube add a piece of sodium the size of a pea. Close 
the tube with a cork carrying a small drying-tube containing 
calcium chloride, and set aside. Examine in an hour. (£4@.) 


Notrs.—(a) Some tertiary halides are decomposed when treated with 
concentrated sulphuric acid. 

(d) This reaction is useful as a test to distinguish alkyl halides from cer- 
tain halogen derivatives of benzene and other hydrocarbons, which are not 
decomposed readily by alcoholic potassium hydroxide. It is necessary to 
use a solution of potassium or sodium hydroxide free from halogen com- 
pounds. Since the alkalies usually contain chlorides, the solution is pre- 
pared by using absolute alcohol in which sodium chloride and potees up 
chloride are insoluble. 


133. Preparation of Ethyl Iodide from Ethyl Alcohol and 
Hydriodic Acid.—Place 60 grams of a strong solution of hydriodic 
acid and water (the constant-boiling mixture, which contains 57 
per cent hydrogen iodide, and has the specific gravity 1.7) in a 


100 EXPERIMENTAL ORGANIC CHEMISTRY 


200 ce. distilling flask connected with a condenser through which 
a rapid stream of cold water is passing. Connect an adapter 
to the condenser and use as a receiver a flask surrounded by 
water. Close the distilling flask with a stopper bearing a drop- 
ping funnel (see Fig. 16, page 27), the end of which reaches to 
the bottom of the flask. Heat the hydriodic acid to boiling, and 
drop in through the funnel 10 grams of alcohol at about the same 
rate as that at which the iodide distils over (about 1 drop per — 
second). Add water to the receiver, shake, and decant off the 
water into a beaker. Separate the iodide by means of a separa- 
tory funnel, place it in a small distilling flask, and add about 
one-fourth its volume of anhydrous calcium chloride. Cover 
the sidé-arm of the flask with a cork, and place one in the neck 
of the flask. Let the iodide stand until it is quite clear, and distil 
from a water-bath. Calculate the percentage yield obtained. 

Ethyl iodide boils at 72.3°, and has the specific gravity 1.944 
(14°). The yield in this preparation is about 90 per cent of the 
theory, calculated from alcohol; a slight excess of the hydriodic 
acid is used. 


134. Preparation of Isoamyl Bromide from Isoamyl Alcohol 
and Hydrobromic Acid.—Distil slowly from a 250 ce. distilling 
flask, connected with a water condenser, a mixture of 20 grams of 
isoamyl alcohol and 76 grams of the constant-boiling mixture 
of hydrobromic acid and water, which contains 48 per cent of 
acid and has the specific gravity 1.49. When the bromide 
ceases to distil over, add water, separate the two layers in a 
separatory funnel, and shake the bromide with twice its volume 
of concentrated hydrochloric acid, which dissolves out from the 
bromide the alcohol that has distilled unchanged. Wash twice 
with water, separate, and dry with calcium chloride. Pour off 
the liquid through a funnel, which contains a bit of cotton wool, 
into a distilling flask and distil. Save the liquid in the flask, and 
put it in the bottle reserved for hydrobromic acid. residues. 
Weigh the product and calculate the yield. 

Isoamyl bromide boils at 118°, and has the specific panies 
1.219 at 15°. The yield is about 60 per cent of the theoretical 
calculated from the alcohol used. 


Notsr.—It is frequently advantageous to prepare the alkyl bromides and 
iodides from the alcohols and aqueous solutions of the halogen acids (the 


HALOGEN COMPOUNDS 101 


so-called constant-boiling mixtures with water). This is particularly the 
case when a very pure product is sought, or when an expensive synthetic 
alcohol is used. In the latter case it is well, in order to increase the yield, to 
use a large excess—two or three times the theoretical amount—of the acid; 
the latter can be recovered readily. In making the lower alkyl halides, a 
good yield can be obtained by using slightly more than the theoretical 
amount of the halogen acid; in the case of the higher alcohols a large excess 
is necessary. The alkyl halides prepared in this way are contaminated in 
certain cases with a trace of an unsaturated hydrocarbon; this can be re- 
moved by shaking them with a dilute solution of potassium permanganate. 


135. Preparation of Chloroform (Section 213).—Place in a 
liter flask 150 grams of fresh bleaching powder and 400 ce. of 
water. Shake vigorously in order to break up the lumps of 
bleaching powder, and connect the flask with a reflux condenser. 
Through the condenser add, drop by drop, from a separatory 
funnel a mixture of 12 grams of acetone and 50 cc. of water. 
Arrange the flask for distillation with steam (see §28, page 18) 
and distil as long as the chloroform comes over. Wash the 
chloroform by decantation twice with water, separate, and place 
it in a small dry distilling flask with anhydrous calcium chloride. 
When the liquid is quite clear and no drops of water are visible, 
distil from a water-bath, using a condenser. Weigh the product, 
determine its specific gravity ($56, page 37), and calculate the 
percentage yield obtained. 

Chloroform boils at 61° and has the specific gravity 1.498 at 
15°. The yield should be about 20 grams. 


Norre.—The yield of chloroform is affected greatly by the quality of the 
bleaching powder used. The acetone is added slowly as the reaction is a 
vigorous one, and frothing is apt to occur if the flask becomes hot. 


136. Properties of Chloroform (Section 213).—(a) Odor and 

solubility of chloroform.—Note the odor of chloroform and de- 
termine whether it is soluble in water, ether, alcohol, benzene, 
petroleum ether, and concentrated sulphuric acid. 
(6) Chloroform as a solvent—Determine if the following sub- 
stances are soluble in chloroform: iodine, butter, vaseline, olive 
oil, a bit of black rubber tubing. In the latter case, let the 
liquid stay in contact with the rubber for some time; then pour 
off the liquid on to a watch-glass, and let it evaporate. 

(c) Inflammability of chloroform.—Try to ignite some chloro- 


102 EXPERIMENTAL ORGANIC CHEMISTRY 


form. Light a match and pour on the flame the vapor from 
some chloroform which has been heated to boiling. 

(d) Test for chlorine in chloroform.—Apply the test for halogen 
with a copper wire ($60, page 40). Shake some chloroform with 
a little water and test the aqueous solution with silver nitrate. 
If silver chloride is formed wash the chloroform until the wash- 
water no longer reacts with silver nitrate. Separate the chloro- 
form with a pipette, dissolve it in alcohol and add an alcoholic 
solution of silver nitrate. 

(e) Decomposition of chloroform in sunlight.—Place some chloro- 
form which contains no free hydrochloric acid in a test-tube, 
close the tube with a stopper, and allow it to stand several days 
in a place where it will be in a strong light. Note the odor, shake 
with water, and test the aqueous solution with silver nitrate. 

(f) Chloroform and sodium hydroxide.—Heat a few drops of 
chloroform for 1 minute with about 5 ce. of a very dilute solution 
of sodium hydroxide free from chlorides. (Hq.) Test half of 
the solution for chloride. Neutralize carefully the rest of the 
solution with hydrochloric acid, add 5 drops of a dilute solution 
- of mercuric chloride and heat. (See note below and experiment 
87d, page 62.) 

(g) Carbylamine reaction (Srction 198).—Hoop.—Warm to- 
gether 1 drop of aniline, which is a primary amine and has 
the formula CsHsNH2, 1 drop of chloroform, and 1 ce. of an 
alcoholic solution of potassium hydroxide. (Kq.) On account 
of the very disagreeable odor produced, the test-tube should be 
washed in the hood with concentrated hydrochloric acid. 

(h) Oxidation of chloroform.—Heat together a few drops of 
chloroform, a small crystal of potassium bichromate, and 2 ce. 
of concentrated sulphuric acid. (H#q.) Cautiously note the 
odor of the gas formed. 

Notr.—(f) The reaction between chloroform and sodium hydroxide is 
analogous to that between the alkali and other halogen compounds. In 


this case the three chlorine atoms are replaced by hydroxyl groups; the 
resulting compound loses water and formic acid is produced: 


CHCl; + 3NaOH = CH(OH); + 3NaCl 
O 


ane ! 
COH = HC—OH + H,0 
NOH 
HCOOH + NaOH = HCOONa + H,O. 


HALOGEN COMPOUNDS 103 


137. Preparation of Ethylene Bromide (Sections 216, 29).— 
(a) With phosphorus pentoxide as dehydrating agent.—Weigh di- 
rectly into a 200 cc. distilling flask 40 grams of phosphorus 
pentoxide; close the side-arm of the flask with a stopper and 
connect the flask with a reflux condenser (see Fig. 14, page 25). 
Place the flask in cold water, and with constant shaking add 
slowly through the condenser 30 grams of alcohol. Heat the flask 
carefully with a free flame until the phosphorus pentoxide has 
dissolved. Remove the condenser, place the flask on a wire 
gauze at such a height that it can be heated with a burner, 
close with a stopper, and connect with the absorption apparatus 
which is arranged as follows: Fit three 8-inch test-tubes with 
tightly fitting stoppers each containing two holes. The stoppers 
should be covered with paraffin. This can be done by inserting 
them into paraffin melted in an evaporating dish. As the appara- 
tus must be tight it is advisable to use stoppers of rubber. Pre- 
pare three tubes bent at a right angle of such a length that when 
passed through the holes in the stoppers they will extend to the 
bottom of the test-tubes; also three shorter right-angle tubes 
which just pass through the stopper. Put one long and one short 
tube into each stopper, and connect the tubes in such a way that 
a gas passing through the train when the test-tubes are in place, 
will pass to the bottom of each test-tube through the long tube. 


- Put 10 ce. (80 grams) of bromine in each of two of the test-tubes, 


and cover with a layer of water about 2 cm. high, which largely 
prevents the volatilization of the bromine as the gas passes 
through. The three test-tubes are now placed in beakers con- 
taining cold water, and connected with the distilling-flask, the 
empty tube which serves to condense any liquid which distils 
over, being placed next to the flask. In order to prevent bromine 
from getting into the air, connect a drying tube containing soda- 
lime with the tube farthest removed from the distilling flask. 
Test the apparatus to see if all joints are tight. 

Heat the flask cautiously at first and then to such a temperature 
that ethylene is given off freely. After the gas begins to come 
off the apparatus needs little attention if it is so placed that the 
flameis not ina draught;if thisis the case, use a chimney so that 
a steady heat may be obtained. Heat as long as ethylene is 
formed; from one-half hour to an hour is usually sufficient. If 


104 EXPERIMENTAL ORGANIC CHEMISTRY 


the bromine has not been used up when the ethylene ceases to be 
evolved, remove the tubes containing ethylene bromide, and under 
the hood transfer the liquids to a flask. Wash by decantation 
with a dilute solution of sodium hydroxide until the heavy oil 
is colorless, and then once with water. Separate the bromide, 
and dry it with calcium chloride. After standing an hour or 
more, until the liquid is clear and no water is visible, filter through 
a funnel, containing a bit of cotton wool, into a small distilling 
flask. Distil, using a thermometer and water condenser, and 
collect the fraction which boils at 180°-132°. Calculate the per- 
centage yield both from the alcohol and bromine used. 

Ethylene bromide melts at 8.4° and boils at 132°, and has the 
specific gravity of 2.189 at 15°. The yield in this preparation 
is about 55 grams. 

(b) With sulphuric acid as dehydrating agent—Mix cautiously 
in a 1 liter round-bottomed flask 90 cc. of alcohol and 135 ce. 
of concentrated sulphuric acid; then add about 50 grams of 
coarse sand and about 5 grams of aluminium sulphate. Place 
the flask on a wire gauze and connect it by means of a tightly 
fitting stopper, preferably one of rubber, with an absorbing train 
of test-tubes like that described in (a) above. In this case use 
four test-tubes which contain, respectively, beginning with the 
one nearest the flask, 20 cc. of a dilute solution of sodium hy- 
droxide, 20 cc. of concentrated sulphuric acid, 10 ec. of bromine 
covered with water, and 10 cc. of bromine covered with water. 
Attach a drying tube containing soda-lime to the last tube. 
Place all of the tubes in cold water. Make a test to determine if 
all joints in the apparatus are tight. 

Heat the flask at the lowest temperature at which ethylene is 
freely evolved. It is very essential to avoid over-heating, which 
results in frothing and the liberation of carbon. If this occurs, 
the contents of the flask should be poured out and ethylene should 
be prepared from a new mixture. When the bromine is decolor- 
ized, treat the product as directed in (a) above. 

The yield is about 55 grams. 

Notr.—Sand is added to the flask to distribute the heat more evenly and, 
thus, to assist in preventing frothing. In the presence of aluminium sul- 
phate, the decomposition of alcohol into ethylene takes place at about 140°, 


whereas in the absence of the sulphate a temperature of about 180° is re- 
quired. At the lower temperature carbonization is not apt to occur. 


HALOGEN COMPOUNDS 105 


AcyL CHLORIDES 


138. Preparation of Acetyl Chloride (Smcrion 219).—Connect 
a 200 cc. dry distilling flask with a separatory funnel and a con- 
denser; for use as a receiver, attach to the latter, by means of a 
tightly fitting cork, a 200 ce. distilling flask or filter-bottle. Con- 
nect to the side-arm of the receiver a drying tube containing cal- 
cium chloride, which serves to protect the distillate from moisture. 
As a large quantity of hydrochloric acid is set free during the 
reaction between acetic acid and phosphorus trichloride, the dry- 
ing tube should be fitted with a glass tube which reaches to just 
above the surface of some water contained in a flask. When the 
apparatus is arranged, place a water-bath containing cold water 
in such a position that the bulb of the distilling flask is covered 
with water. Put 50 grams of glacial acetic acid in the flask, and 
run in slowly through the funnel 40 grams of phosphorus trichlo- 
ride. The latter should be weighed and transferred to the funnel 
in the hood. When the phosphorus trichloride has been added, 
heat the water in the bath to 40°—-50°, until the evolution of hydro- 
chloric acid slackens and the liquid has separated into two layers; 
then heat the water to boiling as long as any distillate comes over. 
Redistil the distillate, using a thermometer, a condenser, and a 
receiver protected from the air as directed above. Collect the 
fraction which boils at 50°-55°. Weigh the product, and cal- 
culate the theoretical yield and the percentage of this obtained. 

Acetyl chloride boils at 51°. The experiment should yield 
about 40 grams. 


139. Properties of Acetyl Chloride (Section 220).—(a) Acetyl 
chloride aad water.—Cautiously add about 0.5 cc. of acetyl chlo- 
ride to 2 ce. of ice-water. Observe if two layers form, and then 
shake carefully. (Kq.) 

(b) Acetyl chloride and alcohol.—Cautiously add acetyl chlo- 
ride, drop by drop, to 2 cc. of alcohol as long as reaction takes 
place. Is hydrogen chloride given off? Pour the product into 
5 ec. of water, shake and note the odor. (Kq.) 

(c) Acetyl chloride and an amine.—Add to 5 drops of aniline, 
CseHsNHz, acetyl chloride, drop by drop, until reaction ceases. 
(Hq.) Add to the tube 10 cc. of water, heat to boiling, and filter 
hot. Set the tube aside to cool. 


CHAPTER XI 
COMPOUNDS CONTAINING TWO UNLIKE SUBSTITUENTS 


140. Preparation and Properties of Trichloracetic Acid (Sxc- 
TION 231).—(a) Hoop.—In a 250 cc. flask place 25 grams of chloral 
hydrate and add 15 cc. of fuming nitric acid (sp. gr. 1.5). Heat 
the flask over a small flame until reaction begins; then remove the 
flame. When the reaction has apparently ceased, heat gently 
until the liquid becomes almost colorless. (#q.) Transfer 
the liquid to a small distilling flask and distil very slowly, using 
an air-condenser. When the temperature reaches 150°, change 
the receiver, using this time a small distilling flask, and collect 
what comes over up to 200°. Redistil slowly and collect the frac- 
tion boiling at 193°-195°. Weigh the product and calculate the 
percentage yield. 

Trichloracetic acid melts at 55° and boils at 195°. The 
amount obtained in this preparation should be about 10 to 
12 grams. 

(b) Dissolve in a test-tube about 1 gram of the acid in water, 
and add 5 ce. of a dilute solution of sodium hydroxide. Attach 
to the tube by means of a cork a piece of glass tubing about 3 
feet long, clamp the tube over a wire gauze, and heat gently so 
that the solution just boils. At the end of 5 minutes cool the 
tube, examine the contents and note the odor. (£q.) 


141. Preparation and Properties of Lactic Acid (SrcrTion 
239).—(a) In a 750 cc. flask dissolve 50 grams of cane-sugar or 
anhydrous glucose in 500 cc. of water; add 20 cc. of sour milk 
and 20 grams of precipitated calcium carbonate. Set the flask 
in a warm place (temperature about 40°) and allow the fermenta- 
tion to proceed for one week. The flask should be shaken at 
least twice a day. At the end of the time add a small amount of 
calcium carbonate, heat to boiling, filter, pour the solution into a 
flat dish, and let it evaporate spontaneously. Filter off the solid 

106 Ef 


TWO UNLIKE SUBSTITUENTS 107 


by suction, dissolve it in a small amount of boiling water, filter 
if necessary, and set the solution aside to crystallize. Separate 
the crystals as before and let them dry on a porous plate. The 
yield is about 35 grams. 

(b) Lactic acid and ferric chloride: test for an a-hydroxy acid.— 
The solution of lactic acid required for this and the following 
experiments can be made from lactic acid, or prepared from the 
calcium lactate obtained in (a) above, as follows: Dissolve about 
2 grams of the salt in 20 ce. of boiling water and add a dilute 
solution of sulphuric acid, drop by drop, as long as a precipitate 
isformed. If it is difficult to determine when the correct amount 
of acid has been added, filter onto a watch-glass a few drops 
of the solution and add to the filtrate a drop of sulphuric acid. 
If an excess of sulphuric acid has been used, add to the original 
solution a little of a solution of calcium lactate. When all the 
calcium has been precipitated, warm the solution and filter. In 
a small evaporating dish add to 5 ce. of the solution 1 drop of a 
10 per cent aqueous solution of ferric chloride. Repeat the test, 
using 5 cc. of water instead of the solution of the salt. Compare 
the color in the two cases. 

(c) Solubility of lactic acid——Determine whether lactic acid 
can be extracted from water by ether. Describe fully how you 
made the test. 

(d) Application of the todoform reaction to lactic acid.—Deter- 
mine whether lactic acid gives the iodoform reaction (experiment 
81b, page 57). 

Notrre.—(a) The sour milk used in the preparation contains the lactic 
acid bacteria. The milk should be used before the curd has separated. 
The latter is needed for the development of the bacteria during fermenta- 
tion. Calcium carbonate is added to neutralize the lactic acid as it is 
formed, since the fermentation stops if the acid accumulates. Toward the 
end of the fermentation butyric acid is usually formed. The odor produced 
is due to this cause. When the sugar has been fermented the calcium car- 
bonate passes into solution. If there is a large residue at the end of a week 
the milk was not satisfactory. The zinc salt of lactic acid is characteristic. 
It can be prepared by digesting a strong solution of the acid with zinc car- 
bonate, filtering hot, and evaporating to crystallization. 


142. Properties of Tartaric Acid and Tartrates (SrcTIONS 
251-254).—(a) Behavior of tartaric acid and tartrates on heating. 
—Heat a little tartaric acid in a test-tube. Note the change 


108 EXPERIMENTAL ORGANIC CHEMISTRY 


in appearance and the odor produced. What products are 
formed? Repeat, using Rochelle salt. 

(b) Tartaric acid and ferric chloride.—Apply the test for an 
a-hydroxy acid as follows: Dissolve about 0.1 gram of tartaric 
acid in 100 ec. of water. To 20 cc. of this solution add 1 drop of 
a 10 per cent aqueous solution of ferric chloride. Compare the 
color with that produced by adding 1 drop of ferric chloride to 
20 cc. of water, and in a second tube to 20 cc. of water containing 
1 drop of acetic acid. The depth of color can be more readily 
observed by looking down the tubes placed on white paper. 

(c) Potassium salts of tartaric acid.—Make a cold saturated 
solution of tartaric acid by shaking an excess of the acid with 
5 ce. of water. Decant off the liquid and add, drop by drop, a 
10 per cent solution of potassium hydroxide, until a crystalline 
precipitate forms (H£q.); then add an excess of the solution of 
potassium hydroxide. (q.) 

(d) Calcium tartrate: test for tartrates—Neutralize a solution 
of tartaric acid or of cream of tartar with ammonia, and add 
to the solution 1 cc. of a solution of calcium chloride. (Kq.) 
If a precipitate of calcium tartrate does not appear, rub a glass 
rod against the side of the tube under the surface of the liquid. 
Filter off the precipitate, and pour 5 cc. of a solution of sodium 
hydroxide through the filter into a clean test-tube. Heat the 
filtrate to boiling. This behavior of tartaric acid is charac- 
teristic, and is used in the identification of the acid and its soluble 
salts. 

(e) Reducing action of tartrates—To a dilute solution of 
Rochelle salt or sodium tartrate contained in a test-tube, which 
has been cleaned by boiling in a solution of sodium hydroxide 
and washing with water, add 1 cc. of a solution of silver nitrate. 
Dissolve the precipitate by adding ammonia, drop by drop, 
avoiding excess, and place the tube in hot water. Compare the 
results with those obtained with formaldehyde (experiment 106d). 
Is the formation of a silver mirror a positive test for an aldehyde? 

(f) Fehling’s solution—Add to 1 ce. of a solution of copper 
sulphate 5 cc. of a solution of sodium hydroxide (£q.); then add 
a solution of Rochelle salt or of sodium tartrate until the precipi- 
tate dissolves. (Hq.) Repeat, using glycerine in placeof Rochelle 
salt. It is necessary to have a large excess of sodium hydroxide. 


TWO UNLIKE SUBSTITUENTS 109 


What organic compounds other than acids dissolve copper hy- 
droxide? Determine if Rochelle salt will dissolve the hydroxides 
of iron and aluminium. 


Nortres.—(b) This test for e-hydroxy acids must be made in the cold, as a 
solution of ferric chloride alone develops a decided yellow tint on being 
heated. In applying the test to an unknown substance a very dilute solu- 
tion should be used, and the color developed should be compared with that 
formed in a solution of equal concentration of an a-hydroxy acid (tartaric 
acid). Many solutions of hydroxyl compounds when sufficiently concen- 
trated give a yellow color with ferric chloride. The colors given by poly- 
basic and ketonic acids are usually more intense or of a different shade from 
those given by a-hydroxy acids 

(d) In making this test the calcium tartrate is usually filtered off before 
solution in sodium hydroxide, since the carbonate that the alkali contains 
produces a precipitate of calcium carbonate, which is insoluble. The 
presence of ammonium salts should be avoided in making the test, as they 
interfere with the precipitation of calcium tartrate. 


143. Properties of Citric Acid and Citrates (SmcTion 258).— 
(a) Decomposition of citric acid by heat.—Heat a little citric acid 
in a dry test-tube. Note the odor. What acids are present 
among the products of decomposition when citric acid is heated? 
(See Section 113.) 

(6) Calcium citrate: test for citric acid.—Dissolve about 1 gram 

of citric acid in about 50 cc. of water. Neutralize 5 cc. of the 
solution with ammonia, avoiding an excess of the latter. If too 
much has been added, add a little of the solution of the acid 
until the reaction is neutral or slightly acidic. To the solution 
of ammonium citrate add about 2 cc. of a 10 per cent solution of 
calcium chloride. Is a precipitate formed? Compare the be- 
havior of tartrates. Heat the solution to boiling and set aside. 
Examine in a few minutes. A precipitate of tricalcium citrate 
is formed. Is the precipitate of tricalcium citrate crystalline? 
Wash the salt by decantation three times with water, and de- 
termine its solubility in a solution of sodium hydroxide. Com- 
pare the result with that obtained with tartrates. Preserve 
the solution of citric acid for experiments (d) and (e) below. 

(c) Presence of citric acid in lemon juice.—Test 5 ce. of lemon 
juice or pineapple juice for citric acid as described above. Add 
ammonia to the filtered juice but have it slightly acid when mak- 
ing the test. 


110 EXPERIMENTAL ORGANIC CHEMISTRY 


(d) Reducing power of citrates—Neutralize 5 cc. of the solu- 
tion of citric acid prepared in (6) above with sodium hydroxide, 
add 1 cc. of a solution of silver nitrate, and then ammonia drop 
by drop, until the precipitate is dissolved. Place the tube in 
boiling water for two minutes. Is a mirror of silver formed? 
(Compare with tartrates.) Heat the solution to boiling for two 
minutes. Set aside and examine later. 


(e) Reduction of ferric citrate by light—Add to 5 cc. of a solution . 


of ferric chloride, until a clear green color is formed, a solution 
of ammonium citrate, prepared by neutralizing a solution of 
citric acid with ammonia. Moisten a piece of paper with the 
solution, dry the paper in the dark in your desk and then expose 
it to sunlight under a piece of thick paper in which a design has 
been cut. At the end of 10 minutes place the paper in a dilute 
solution of potassium ferricyanide. Write the formulas for all 
the substances involved in the reactions, starting with ferric 
chloride. 

Notre.—(b) In the presence of a large excess of sodium hydroxide, cal- 


cium chloride gives a precipitate in the cold with solutions of alkali citrates. 
Calcium citrate is soluble in acetic acid (calcium oxalate is insoluble). 


144, Preparation of Acetoacetic Ester (Smction 263).—(a) 
The ethyl acetate to be used in this preparation must be dried 
and distilled just before use. Place 250 cc. of ethyl acetate, 
which should be neutral, in a 500 cc. flask, and add anhydrous 
calcium chloride (about one-fourth of the volume of the ester). 
Let the mixture stand over night or longer. Distil directly on 
a water-bath from the calcium chloride, and collect the distillate 
in a dry receiver which is protected from the moisture of the air. 
Provide a reflux condenser for a 500 cc. flask, which has been 
carefully dried, and set the flask in cold water. Add 200 grams 
of the dried ethyl acetate and 20 grams of sodium in the form of 
wire or very thin shavings (see §41, page 27). Connect the 
condenser with the flask. When the evolution of hydrogen 
ceases, heat the flask on a water-bath at such a temperature 
that the contents boil gently. When all the sodium has dis- 
solved, about 3 hours being required, cool the flask, and add 
slowly a mixture of 1 part of concentrated hydrochloric acid and 
4 parts of water, until the solution shows an acid reaction after 
having been shaken thoroughly. Add an equal volume of a 


| 
: 


TWO UNLIKE SUBSTITUENTS 111 


saturated solution of sodium chloride, transfer to a separatory 
funnel, and separate the ester as carefully as possible from water. 
Shake the ester with a little anhydrous calcium chloride until it 
becomes clear and no water can be seen, pour off from the drying 
agent, and distil the liquid slowly from a flask provided with a 
small Hempel tube (see Fig. 5, page 11). Discard the distillate 
which boils up to 160°; collect the following fractions: 160°-175°, 
175°-185°, 185°-200°. The fraction boiling at 175°-185° is 
nearly pure acetoacetic ester. By redistilling the other fractions 
a further quantity can be obtained, but as acetoacetic ester de- 
composes slowly on boiling at atmospheric pressure, it is not 
advisable to carry out an extended fractionation. If a better 
yield is desired, the product of the reaction may be distilled under 
diminished pressure. 

Acetoacetic ester boils at 182° at 760 mm., 74° at 14 mm., 
and 88° at 29 mm. It has the specific gravity of 1.03 at 15°. 
The yield in this preparation should be 35-40 grams. 

(b) Compare the solubility of acetoacetic ester in water and 
in a solution of sodium hydroxide. Explain. 

(c) Dissolve a few drops of acetoacetic ester in 1 cc. of alcohol 
and add a few drops of a solution of ferric chloride. What does 
the result indicate? 


145. Acetoacetic Ester Synthesis (SecTIon 264).—(a) Prepara- 
tion of ethylacetoacetic ester—Into a 500 ce. flask place 60 ec. of 
absolute alcohol. Weigh 4.6 grams of sodium and cut it into five 
or six pieces. Hold the flask under running water and add one 
piece of the metal. At the end of about a minute, when the vio- 
lent reaction ceases, add the rest of the sodium and connect the 
flask by means of a tightly fitting cork or rubber stopper with 
a long reflux condenser through which a rapid stream of water 
is passing. When the metal has dissolved add slowly through the 
condenser 26 grams of acetoacetic ester, and then 24 grams of 
ethyl bromide. Heat slowly to boiling on a water-bath until a 
drop of the solution when mixed with a drop of water does not 
show an alkaline reaction. Avoid too rapid heating at first, as 
the reaction may become violent and ethyl bromide be lost. 
The time required is about 2 hours. When the reaction is com- 
plete, distil off the excess of alcohol on the water-bath, add 50 


112 EXPERIMENTAL ORGANIC CHEMISTRY 


ec. of water to the residue, and shake until the salt has dissolved. 
Separate the oil in a small separatory funnel, dry over calcium 
chloride and distil. Collect the portion which boils at 192°—200°. 
Calculate the percentage yield. Write equations for all the 
reactions involved. 

Ethylacetoacetic ester boils at 198°. The yield should be 
about 22 grams. 

(b) Hydrolysis of ethylacetoacetic ester (SECTION 264).—Ketone 
hydrolysis —In a 500 ce. flask dissolve 10 grams of sodium hy- 
droxide in 100 cc. of water, add 15 grams of ethylacetoacetic 
ester, and connect with a reflux condenser. Place the flask in 
a bath containing boiling water for 2 hours. Cool, place the 
contents of the flask in a small separatory funnel, separate the 
oil, and dry over calcium chloride. Pour off the oil from the 
drying agent after a few hours and distil it. Collect what boils 
at 98°-103°. 

Methyl propyl ketone, the product of the reaction, boils at 
102°. The yield obtained is about 60 per cent of the theoretical. 

Acid hydrolysis.—In a small flask dissolve 5 grams of sodium 
hydroxide in 15 cc. of water and add 5 grams of ethylacetoacetic 
ester. Shake vigorously and connect the flask with a reflux 
condenser. Place the flask in boiling water for 2 hours. At the 
end of this time distil with steam (§28, page 18) until about 
100 cc. of water have passedover. (Whatelse passesover?) Cool 
the flask through which steam has been passed, make the contents ~ 
acid to litmus with dilute sulphuric acid, and then add about 
50 cc. of the acid in excess to liberate the organic acids formed 
in the hydrolysis. Distill again with steam into a clean receiver 
until about 300 cc. of water have passed over. Note the odor of 
this second distillate. Neutralize the latter with sodium hydrox- 
ide and evaporate to dryness. The residue is a mixture of 
sodium acetate and sodium butyrate. Put a little of the solid 
on a watch-glass and add a few drops of concentrated sulphuric 
acid. Note the odor. Add to this a few drops of alcohol, and 
after warming gently note the odor. 

The presence of butyric acid in this mixture can be shown in 
another way as follows: Dissolve about 0.5 gram of the salt in 
5 cc. of water. Acidify with dilute sulphuric acid, warm to 
liberate any carbon dioxide present. Neutralize with ammonia, 


TWO UNLIKE SUBSTITUENTS 113 


and adda solution of calcium chloride. If aprecipitate is formed, 
it is calcium butyrate. Filter this off and heat the filtrate to 
boiling. Since calcium butyrate is slightly less soluble in hot 
water than in cold, the cold saturated solution deposits a pre- 
cipitate when heated to boiling. Write equations for all reactions 
involved in the experiment. 


Notr.—(a) If the solution of sodium acetoacetate and ethyl bromide 
does not become neutral on boiling, it is evident that some of the latter. has 
been lost. This may result from too active boiling at first or there may have 
been a leak in the stopper connecting the flask with the condenser. If 
this occurs add more of the bromide and heat again. 


146. Properties of Chloral (Section 267).—(a) Preparation 
from chloral hydrate——Shake in a small test-tube about 3 grams 
of chloral hydrate and 3 cc. of concentrated sulphuric acid. (K4@.) 
Separate by means of a pipette the oil which floats on the sul- 
. phuric acid, and add it to one-half its volume of water. (Eq.) 

(b) Test for the aldehyde growp.—Determine whether chloral 
hydrate forms a silver mirror with ammoniacal silver nitrate 
(experiment 106d, page 81), and whether it produces a color 
with Schiff’s reagent. . 

(c) Decomposition of chloral hydrate by alkalies.—Dissolve 
about 1 gram of chloral hydrate in water and add a solution of 
sodium hydroxide. (Hgq.) Test for chloroform. 


CHAPTER XII 
CARBOHYDRATES 


147. Properties of Dextrose (Sections 282-284).—(a) Taste 
and solubility of dextrose—Taste equal amounts of dextrose 
and cane-sugar. Determine whether dextrose is soluble in the 
following liquids: water, alcohol, and ether. 

(b) Presence of alcoholic hydroxyl groups in dextrose.—In a 100 
cc. bottle shake 10 cc. of a 10 per cent solution of dextrose with 
2 cc. of benzoyl chloride and 25 cc. of a 10 per cent solution of 
sodium hydroxide. Shake vigorously until the odor of the ben- 
zoyl chloride disappears. Write the structural fromula of the 
compound formed. 

(c) Dextrose and copper hydroxide.—Precipitate copper hy- 
droxide by adding 5 cc. of a solution of sodium hydroxide to 
1 ec. of a solution of copper sulphate, and then add 5 ce. of a 
strong solution of dextrose (about 20 per cent) and shake. It is 
necessary to have a large excess of the alkali present. Compare 
with experiment 142f, page 108. Heat the solution nearly to 
boiling. | , 

(d) Dextrose and alkalies ——Boil 10 cc. of a 10 per cent solution 
of dextrose with 5 cc. of a solution of sodium hydroxide. Com- 
pare the result with that obtained with aldehyde and sodium 
hydroxide (experiment 108d, page 83). 

(e) Dextrose and Schiff’s reagent—Determine whether dex- 
trose produces a color with Schiff’s reagent (experiment 108A, 
page 83). 

(f) Reducing action of dextrose: silver mirror.—Test a dilute 
solution of glucose with an ammoniacal solution of silver nitrate 
or with Tollen’s reagent (experiment 106d, page 81). 

(g) Reducing action of dextrose: Fehling’s solution.—Test a 
dilute solution of dextrose with Fehling’s solution. 

(h) Preparation of dextrosazone.—Dissolve 1 gram of dextrose 
in 20 cc. of water and add 2 grams of phenylhydrazine hydro- 

114 


- ne i ae 


+ = 





CARBOHYDRATES 115 


chloride, which should be colorless (see note), and 3 grams of 
hydrated sodium acetate. Heat the solution by placing the 
flask in boiling water for 10 minutes. Cool under running water, 
filter by suction, and wash the crystals with cold water. Redis- 
solve the crystals in the smallest possible amount (about 20 cc.) 
of boiling 50 per cent alcohol. Filter the hot solution, cool in 
running water, filter off the crystals, and dry them on a porous 
plate, and finally at 100°. Determine the melting-point of the 
crystals in a bath, the temperature of which is rising rapidly, as 
dextrosazone decomposes slowly when heated. The melting- 
point of dextrosazone is 204°-205°. 


Nores.—(b) The insoluble compound formed is a pentabenzoate of 
dextrose which is produced as the result of the replacement of the hydro- 
gen atoms of the hydroxyl groups in dextrose by the benzoyl radical present 
in benzoyl chloride, CsH;COCIl. The test is an application of the Baumann- 
Schotten reaction (see SecTIon 463). 

(c) Polyatomic alcohols and compounds related to them, such as the 
sugars, dissolve the hydroxides of certain heavy metals. Compounds simi- 
lar to that present in Fehling’s solution (Suction 252) are formed. The 
sugars also form soluble compounds with calcium and barium hydroxides. 

(e) Although many of the carbohydrates contain the aldehyde group, 
they do not produce a color with Schiff’s reagent. 

(h) Phenylhydrazine and its salts decompose rapidly when exposed to 
air and to light. Pure compounds must be used in the preparation of osa- 
zones. ‘The phenylhydrazine can be dissolved in an excess of acetic acid, 
just before use, or the hydrochloride and sodium acetate may be used. The 
pure hydrochloride can be prepared as follows: Redistil the phenylhydra- 
zine if it is colored. Dissolve the compound in 12 times its volume of 
alcohol, and add pure concentrated hydrochloric acid as long as a precipi- 
tate isformed. Filter off the precipitate by suction, and wash it with alco- 
hol until it is colorless. Wash twice with ether. If the salt is not to be 
used immediately, dry it in the air for half an hour, and then for 1 hour at 
100°. Place the salt in a tightly stoppered bottle of brown glass. 


MONOSACCHARIDES AND DISACCHARIDES 


148. General Reactions and Properties of the Sugars.—All 
the experiments given in this section should be performed in 
each case with samples of dextrose, levulose, maltose, lactose, and 
sucrose. 3 

(a) Molisch reaction for carbohydrates (Section 313).—Place 
a piece of the carbohydrate about the size of a mustard seed in 


116 EXPERIMENTAL ORGANIC CHEMISTRY 


10 drops of water, and add 2 drops of a 10 per cent solution 
of a-naphthol in chloroform. Allow 1 cc. of pure concentrated 
sulphuric acid to flow, from a pipette, down the side of the inclined 
tube so that two layers are formed. A pipette for this purpose 
may be made by drawing out a piece of glass tubing to a fine open- 
ing at oneend. Observe what happens in a few seconds. Shake 
and allow the mixture to stand 2 minutes; note the color. 
Dilute with water, note the change, add an excess of ammonia, 
and note the color. 

(b) Solubility of sugars——Determine whether the carbohy- 
drates are soluble in water, in alcohol, and in ether. Dry test- 
tubes should be used when the solubilities in alcohol and ether 
are studied. 

(c) Reduction of silver salts—Determine whether dilute solu- 
tions of the carbohydrates give a mirror with an ammoniacal 
solution of silver nitrate or with Tollen’s reagent. (See experi- 
ments 106d, page 81, and 108g, page 83.) 

(d) Reduction of Fehling’s soluttons.—Dissolve about 0.1 gram 
of the carbohydrate in 5 cc. of water, and add 3 cc. of each of 
the solutions which combined make Fehling’s solution. (See 
Appendix for the composition of this solution.) Heat to boiling. 

(e) Fermentation of carbohydrates.—Fill fermentation-tubes 
with 10 per cent solutions of the carbohydrates. Add to each 2 
ec. of a mixture made by rubbing one-quarter of a yeast-cake 
with 10 cc. of water. Label the tubes, and place them in a ther- 
mostat at 30°-35° until the next exercise. Test the gas formed. 
Which of the sugars are fermentated by common yeast? 

(f) Formation of osazones.—Place in separate test-tubes 5 ce. 
of 2 per cent aqueous solutions of the five carbohydrates; label 
the tubes. Mix intimately 1.3 grams of colorless phenylhydra- 
zine hydrochloride and 2 grams of crystallized sodium acetate. 
Divide the mixture into 5 equal parts and put one of the parts 
into each of the five tubes. Note the time and place the tubes 
in a beaker containing boiling water and heat for one-half hour. 
Shake the tubes when the salts have dissolved in order to mix the 
solution. Examine the tubes frequently and note the order in 
which the precipitates first appear. At the end of one-half hour 
place the tubes in a rack and see if any osazones crystallize out on 
cooling slowly. Make a full record of the results of the experi- 


CARBOHYDRATES Ez 


ment. Examine all the osazones under a high-power microscope, 
and sketch the crystals. 

(g) Summary of results——Prepare a table in which are tabu- 
lated the results of experiments a, 6, c, d, e, and f above. 
State how you could distinguish each one of the five sugars 
from the others. 


149. Properties of Sucrose (Sxctions 296-297).—(a) Prepa- 
ration of caramel.—Place about 2 grams of sucrose in a test-tube 
and heat it for 15 minutes in an oil-bath at 210°. Taste the 
product and determine if it is soluble in water. 

(b) Sucrose and sulphuric acid—Add to about 2 grams of 
sugar 2 cc. of water and then 5 cc. of concentrated sulphuric 
acid. If no marked change occurs heat gently. Repeat using 
dextrose instead of sucrose. 

(c) Sucrose and alkalies—Heat 5 cc. of a solution (about 10 
‘per cent) of sucrose with a solution of sodium hydroxide. Is the 
solution highly colored? Compare with the results obtained 
with dextrose. What conclusion can be drawn from the experi- 
ment? What other tests lead to the same conclusion? (See 
experiment 148c, d, f, page 116.) 

(d) Formation of tricalcium saccharate-—Shake 10 cc. of a 20 
per cent solution of sucrose with an excess of milk of lime, which 
can be prepared by slaking a little quicklime and grinding the 
calcium hydroxide with enough water to make a thin paste. Fil- 
ter the solution and heat it to boiling. (Hq.) 

(e) Inversion of sucrose—Boil for 5 minutes a solution of 
about 0.2 gram of sucrose in 10 cc. of water to which has been 
added 1 cc. of dilute hydrochloric acid. Neutralize the solu- 
tion with sodium hydroxide, and test for a reducing sugar with 
Fehling’s solution. 


150. Isolation of Lactose from Milk (Srction 300).—In a 
beaker heat 200 cc. of milk to about 50°, and add a dilute 
solution of acetic acid as long as a precipitate is formed (about 
5 cc. of a 10 per cent solution of the acid). Stir until the casein 
collects into a ball; remove this and neutralize the solution with 
a dilute solution of sodium hydroxide. Make the solution 
weakly acidic by adding 2 or 3 drops of very dilute acetic acid. 
Heat the solution to boiling and add about 1 gram of precipi- 


118 EXPERIMENTAL ORGANIC CHEMISTRY 


tated calcium carbonate. Stir thoroughly and filterhot. Evapo- 
rate the solution to about 40 cc., cool, add 3 volumes of alcohol, 
and filter. Set aside the solution in a shallow dish until the next 
exercise. Filter off the crystals of lactose by suction and wash 
them with alcohol. Dry the crystalsin the air. Taste the sugar. 

Note.—The procedure adopted in this experiment is designed to bring 
about the precipitation of the proteins the milk contains. The solution is 
heated with calcium carbonate before evaporation in order to neutralize 
the free acid present, and thus largely prevent the hydrolysis of lactose 
which takes place when the sugar is heated with water in the presence of 
acids. 

151. Oxidation of Lactose (see galactose, Sections 291 and 
259).—Heat 10 grams of lactose on the water-bath with about 
four times its weight of concentrated nitric acid (28 ec.) until 
the brown oxide of nitrogen is formed. Keep the mixture at 
70°-80° until the evolution of gas ceases. Dilute the solution 
with one-half its bulk of water and let it stand until cold. Mucic 
and oxalic acids crystallize out. Filter, save the filtrate, and 
wash the crystals with warm alcohol to dissolve the oxalic acid, 
and then twice with a small amount of cold water. Recrystallize 
the residue, mucic acid, from a small amount of boiling water. 

Neutralize the filtrate obtained above with solid potassium 
carbonate, strongly acidify with glacial acetic acid, and let stand 
until crystals of potassium hydrogen saccharate are formed. 
Filter these off and recrystallize them from the smallest possible 
amount of boiling water. 

Dissolve a few crystals of mucic acid in a few drops of a solu- 


tion of potassium hydroxide on a microscope slide. When the — 


solution has evaporated examine the crystals under the 
microscope. The form of the crystals of potassium mucate 
is characteristic. Describe their appearance. 

When the ammonium salt of saccharic acid or of mucic sade is 
heated, pyrrole is formed (Srcrion 559). The latter imparts a 
carmine-red coloration to a pine-wood shaving which has been 
moistened with hydrochloric acid. Test the mucic acid obtained 
in this way as follows: Mix 0.1 gram of the acid with 2 cc. of 
ammonia and evaporate to dryness. Heat the residue strongly 
in a test-tube; during the heating suspend in the tube a soft 
pine splinter hich has been soaked in Cone hydrochloric 
acid for a minute or two. 


Sh ee 


CARBOHYDRATES 119 


POLYSACCHARIDES 


152. Properties of Starches (Sructions 3038, 304).—(a) The 
form of starch grains.—Examine under the microscope and sketch 
the following starches: potato, arrowroot, corn, rice, and wheat. 

(b) Application of the Molisch test for carbohydrates.—Test a bit 
of starch, filter-paper, and gum arabic as described in experiment 
148a, page 115. 

(c) Colloidal solutions: dialysis.—Select a piece of parchment 
paper, about 10 inches square, which contains no small holes. 
Wet the paper thoroughly and form it into a bag of about 100 ce. 
capacity; insert the neck of a small funnel into the mouth of the 
bag and fix it in place by tying a string around it. Fill the bag 
with water, dry it carefully on the outside, and hang it up for 
afew minutes. If the bag leaks it must be discarded and a new 
one made. 

Prepare a starch solution as follows: Grind about 2 grams of 
starch with 10 cc. of cold water, pour the mixture into 300 cc. of 
boiling water, and set aside to cool. Pour the water out of the 
‘parchment bag and fill it half full with the starch solution. Take 
care not to spill any of the solution on the outside of the bag. 
Suspend the bag in a beaker containing about 100 cc. of water. 
The beaker should be of such a size that the water in it and that 
in the solution in the bags are at approximately the same level. 
Set aside until the next exercise and test the water outside the 
bag for starch according to experiment (f) below. 

Prepare a second bag and carry out a similar experiment, using 
a 10 per cent solution of glucose. In this case test the water 
outside the bag for glucose by Fehling’s solution. Explain 
dialysis and state why, by means of it, it is possible to separate 
the polysaccharides from the sugars. 

(d) Starch and Fehling’s solution—Wash about 2 grams of 
starch by decantation twice. Shake up the residue with a little 
water, and pour it into 200 cc.of boiling water. Test about 1 cc. 
of this solution with Fehling’s solution. 

(e) Starch and alkalies—Warm 5 cc. of the solution prepared 
in (c) with 5 cc. of a solution of sodium hydroxide. Compare 
the results with those obtained in the case of a monose (experi- 
ment 147d, page 114). 


120 EXPERIMENTAL ORGANIC CHEMISTRY 


(f) Starch and iodine.—Add to 5 ce. of the solution of starch 
1 drop of a solution of iodine in potassium iodide. Heat the 
solution to boiling, and then cool. 

Shake up a little starch with cold water, filter and add a few 
drops of iodine solution to the filtrate. 

Test solutions of dextrose, sucrose, lactose, and dextrin with 
a very dilute solution of iodine (light straw-yellow in color). 

(g) Hydrolysis of starch: with an acid.—Boil in an Erlenmeyer 
flask about 150 cc. of the starch solution prepared in (c) above 
with 10 cc. of concentrated hydrochloric acid. Every 5 min- 
utes pour out about 2 cc. of the solution, cool, and test with a 
very dilute iodine solution. Describe the colors produced as 
the hydrolysis progresses. When iodine produces no color in the 
solution, neutralize about 5 ce. of it and test with Fehling’s 
solution. 

(h) Hydrolysis of starch: with saliva.—A free flow of saliva is 
easily obtained by chewing some insoluble substance such as 
paraffin. Collect about 40 cc. in this way. Filter the saliva 
through a wet filter. Test a portion of the saliva by allowing a 
piece of red and of blue litmus paper to stay in contact with it 
for 5 minutes. 

Prepare 600 cc. of starch paste, using 25 grams of arrowroot 
starch. (Do this in the usual way, by rubbing the starch with 
a little cold water and pouring the suspension into boiling 
water. Boil for 2 or 3 minutes.) Save one-third of the paste 
for subsequent experiments. When the paste has cooled to 40°, 
mix two-thirds of it with 25 cc. of the filtered saliva and watch 
carefully for changes in consistency and opalescence of the mix- 
ture. At 2-minute intervals remove a few drops to a porcelain 
plate, and test with a very dilute iodine solution. Record the 
time required for the solution to clear and to reach the point 
where it no longer produces a color with iodine. Compare your 
figures with those of your neighbors. Are the salivas equally 
active? 

Evaporate the solution in a casserole to about 100 cc. on the 
steam-bath. (If this point is not reached at the end of the 
exercise, leave the labeled casserole on the steam-bath in the 
care of the instructor.) Filter out the small precipitate of car- 
bonate and cellulose. Pour the solution into 3 volumes of 


CARBOHYDRATES 121 


alcohol to precipitate dextrins. Is the amount large? Filter. 
Evaporate the alcohol and water on the steam-bath to a volume 
of about 50 cc. What is the consistency of the residue? Try 
the reducing power and make an osazone. What is the final 
product of salivary digestion? 


153. Conditions Influencing Salivary Digestion—For the 
following experiments dilute the filtered saliva with 5 volumes 
of water and dilute the starch paste with an equal volume of 
water. 

(a) Temperature—tIn each of four test-tubes put 5 cc. of 
starch paste. Keep two tubes at room temperature, chill the 
third in ice-water, and warm the fourth in a 40° water-bath. 
When the tubes have reached the temperature indicated, add 
to the second, third, and fourth in quick succession 1 ce. each of 
diluted saliva, and to the first 1 cc. of boiled, diluted saliva. 
Maintain the tubes at their respective temperatures. Note the 
time required for each to clear. Apply the iodine test at once 
and at intervals of 5 minutes. After half an hour put the first 
and third tubes in the 40° bath and continue the observations. 
Compare the effect of high and low temperature on the enzyme. 

(b) Acid and alkali.—Neutralize to litmus 5 cc. of filtered 
saliva, using 0.4 per cent hydrochloric acid, and dilute with 
5 volumes of water. Prepare a series of eight tubes containing 
5 ec. each of hydrochloric acid of various percentage strengths: 
0.2, 0.1, 0.05, 0.025, etc. To obtain these dilutions, measure 
10 ce. of 0.2 per cent acid in a graduate, pour half into the first 
tube, fill the graduate to the 10 cc. mark with water, mix, pour 
half into the second tube, and so on. ‘To each tube add 5 cc. of 
starch paste, mix thoroughly, and add to each in quick succes- 
sion 1 cc. of the neutralized saliva. Apply the same tests of 
digestion as were used in previous experiments. What concen- 
tration of acid is inhibitory? Compare your results with those 
of your neighbors. Test each tube with litmus, and with congo 
paper. 

Plan and carry out a similar experiment to determine the effect 
of alkali on ptyalin. Use 1 per cent sodium carbonate for the 
highest concentration of alkali. 

(c) Condition of starch—Test the digestibility of raw starch. 


122 EXPERIMENTAL ORGANIC CHEMISTRY 


Continue the experiment, using a little toluene for antiseptic, 
till the following exercise. What do you infer as to the desira- 
bility of cooking starchy foods thoroughly? 

(d) Specificity—Try the action of saliva on cane-sugar and 
Irish moss. What criterion of digestion. will you use? 


154. Preparation and Properties of Dextrin (Section 305).— 
Heat about 5 grams of starch for one-half hour at 220°-225° in an 
bath or air-bath. Pour the product into a mortar, add 2 cc. of | 
water, and notice the adhesive quality of the mixture. Add 
25 ce. of water and grind with a pestle. If there is a residue of 
starch which has not been converted into dextrin, filter through a 
folded filter. Use 2 ec. of the solution to determine whether 
the product reduces Fehling’s solution. Test 2 cc. of the solu- 
tion with a drop of iodine solution and note the color. 

Add to the rest of the solution three times its volume of alcohol. 
Filter off the precipitated dextrin and wash twice with alcohol. 
Dissolve a little of the precipitate and test its reducing power with 
Fehling’s solution. Determine the color produced by iodine 
solution. How does the color compare with that obtained dur- 
ing the intermediate stages of the hydrolysis of starch by acid 
(experiment 152g, page 120). 


155. Properties of Cellulose (Sections 308-310).—(a) Solu- 
bility in Schweitzer’s reagent.—This reagent is a saturated solu- 
tion of copper hydroxide in a concentrated solution of ammonium 
hydroxide. It can be prepared as follows: Dissolve 5 grams of 
copper sulphate in about 100 cc. of water, and add a solution of 
sodium hydroxide as long as a precipitate is formed. Wash the 
precipitate three times by decantation with 500 cc. of water, 
and then filter through cotton; wash until the wash water is free 
from sulphates. Press out as much water as possible from the 
precipitate. Add to 10 cc. of concentrated ammonia (sp. gr. 0.90) 
the copper hydroxide as long as it dissolves. Add pieces of filter 
paper to the reagent as long as they dissolve, and filter through 
glass wool. Pour the solution into dilute hydrochloric acid. 

(b) Preparation of parchment-paper.—Pour slowly with stirring 
50 cc. of concentrated sulphuric acid into 30 cc. of water. Cool 
the solution to 15° to 20° and immerse in it strips of dry filter- 
paper. At the end of 15 to 20 seconds remove the paper, and 


CARBOHYDRATES 123 


wash it rapidly in running water; immerse the paper in a dilute 
solution of ammonia, and wash again with water. Test the 
toughness of the paper and of a piece of wet filter-paper. Put 
a drop of a dilute solution of iodine in potassium iodide on the 
paper. Hang up a piece of the paper to dry and examine it at 
the next exercise. 

(c) Hydrolysis of cellulose.—Grind in a mortar a pinch of cot- 
ton-wool or a filter-paper with a few drops of concentrated sul- 
phuric acid until a sticky mass is obtained; add 50 cc. of water 
cautiously, and boil the resulting solution for 15 minutes. Neu- 
tralize the solution with sodium hydroxide, and test for a reducing 
sugar with Fehling’s solution. 

(d) Preparation of cellulose acetate (SrcTION 309).—In a small 
beaker place 20 cc. of glacial acetic acid, 3 cc. of acetic anhy- 
dride, 2 drops of pure concentrated sulphuric acid, and 0.5 gram 
of cotton-wool. Press the cotton into the solution, and after a 
few minutes stir it so that most of the air bubbles are removed. 
Cover the beaker with a watch-glass and let it stand over night 
or longer. (Kq.) Pour the solution in a thin stream, and with 
stirring, into 500 cc. of water. Filter, using a large funnel. 
Wrap the cellulose acetate in a piece of cotton cloth (a towel), 
and squeeze out as much water as possible; then set it aside 
until dry. Put about one-half the dry product in a small beaker 
or test-tube and add 10 ce. of chloroform. After standing some 
time the acetate should pass into solution. Pour the solution 
onto a watch-glass and let it evaporate slowly. When the 
chloroform has evaporated, put some water into the watch-glass 
and allow it to stand for a minute or two. Lift the edge of the 
film and remove it slowly from the glass. Dry the film and re-- 
serve it for a future test. Test the solubility of the rest of the 
acetate in glacial acetic acid, in alcohol, and in ether. 

(e) Preparation of cellulose nitrate-——Pour 10 cc. of concen- 
trated sulphuric acid into 10 cc. of concentrated nitric acid. To 
the hot mixture add 0.5 gram of cotton-wool. At the end of 
3 minutes withdraw the nitrated cotton, and remove most of the 
acid adhering to it by pressing it with a glass rod against the side 
of the beaker. Put the cotton into a large amount of cold water. 
Wash for a minute in running water, squeezing out the water 
from time to time, and set aside to dry spontaneously. Hold a 


124 EXPERIMENTAL ORGANIC CHEMISTRY 


small bit of the dry nitrate with tongs, and place it in a flame. 
Test the solubility of a small amount of the product in alcohol. 
Repeat using ether. Ina test-tube cover some of the nitrate with 
a mixture made of equal volumes of alcohol and ether. At the 
end of a few minutes pour off the liquid onto a glass plate or 
watch-glass and let the solution evaporate slowly. Remove the 
film asin (d) aboveand dry. Place the edge of the film in a flame 
and as soon as it begins to burn remove it. Note the rate at 
which the film burns. Repeat using the film made from cellulose 
acetate. Do you observe any difference? 


156. Properties of Pentosans (Srections 295, 310, 557).— 
(a) Tests for lignin.—Dissolve a few drops of aniline in a few 
drops of dilute hydrochloric acid, and dilute with 5 cc. of water. 
Pour one-half of the solution onto a piece of paper made from 
wood-pulp (newspaper) and one-half onto a paper made from 
linen. Repeat the tests using a solution of phloroglucinol in 
dilute hydrochloric acid. : 

(b) Hydroiysis of pentosans.—Boil a little gum arabic or wheat 
bran with 10 ec. dilute hydrochloric acid, and hold over the 
tube a piece of paper which has been dipped into a dilute solu- 
tion of aniline in acetic acid. 


CHAPTER XIII 
COMPOUNDS CONTAINING SULPHUR 


157. Formation of Mercaptan (Srcrion 317).—Hoop.—Warm 
together about 1 gram of potassium ethyl sulphate, 1 gram of 
sodium sulphide, and 2 cc. of water. (Kq.) Note the odor. 


158. Preparation of Potassium and Mercuric Thiocyanates 
(Section 324).—Caution.—Potassium cyanide is poisonous and 
should not be handled with the fingers. Boil together 13 grams 
of potassium cyanide, 6 grams of flowers of sulphur and 50 ce. 
of water, until the sulphur has dissolved. (q.) Filter the 
solution and evaporate to crystallization (§9, page 6). Cool, 
filter off the crystals, dry them, and evaporate the mother-liquor 
again to crystallization. Collect the crystals as before. Weigh 
the product obtained. 

Dissolve a few of the crystals in water, and add the solution 
to a solution of ferric chloride. 

Add a saturated solution of potassium thiocyanate to a satu- 
rated solution of mercuric chloride; filter off the precipitate, 
and press it into cones about 0.5 inch high and set aside to dry. 

Apply a lighted match to the top of a dried cone. 


159. Formation of Potassium Xanthate (Section 325).— 
Make a saturated solution of potassium hydroxide in alcohol by 
warming an excess of the alkali with 15 cc. of alcohol. Cool 
the solution, decant off the clear liquid, and add 8 cc. of carbon 
disulphide. (EKq.) Allow the solution to cool. Filter off the 
crystals, wash them with a mixture of 5 cc. of alcohol and 5 
ec. of ether and dry them. Dissolve a little of the compound 
in water, and add a few drops of a solution of copper sulphate. 
The brownish-black precipitate of cupric xanthate changes 
immediately to yellow cuprous xanthate. 


125 


CHAPTER XIV 
URIC ACID AND RELATED COMPOUNDS 


160. Isolation of Uric Acid from Urine (Szection 333).—Add 
50 cc. of concentrated hydrochloric acid to 500 cc. of urine and 
set aside in a cool place for 24 hours. Pour off the liquid from 
the crystals of uric acid which adhere to the side of the vessel. 
Collect the crystals, dissolve them in the smallest possible amount 
of boiling water, boil with a little bone-black, and filter the solu- 
tion hot. On cooling, colorless crystals of uric acid are obtained. 
Examine them under the microscope and sketch the crystals. 


161. Properties of Uric Acid (Section 333).—(a) Solubility of 
uric acid and its salts—Shake up about 0.01 gram of uric acid 
with about 5 cc. of water. Does the acid dissolve? Add a 
dilute solution of sodium hydroxide, drop by drop, and shake. 
When all the acid has dissolved add a slight excess of dilute 
hydrochloric acid, heat to boiling, filter and set aside. 

(b) To a dilute solution of uric acid in sodium hydroxide add 


a little ammonia, some magnesia mixture, and ammoniacal silver 


nitrate. The gelatinous precipitate formed is silver magnesium 
urate. The insolubility of this salt is utilized in the,separation 
of uric acid from urine. The purine bases in urine give similar 
insoluble salts. 

(c) Reduction of silver nitrate by uric acid.—Dissolve a trace of 
uric acid in a few drops of a solution of sodium carbonate, and 
pour the solution upon a piece of paper moistened with silver 
nitrate solution. The silver salt is reduced to metallic silver. 
This reaction is known as Schiff’s test for uric acid. 

(d) Murewide test for uric acid.—On a small watch-glass moisten 
a few crystals of uric acid with 2 or 3 drops of dilute nitric acid. 
Evaporate to dryness on the steam-bath. Cool and add from 
a glass rod a drop of ammonia. A similar color test is given by 
other purines. 

126 


~~ 2. 2 1. me 


URIC ACID AND RELATED COMPOUNDS 127 


162. Isolation of Caffeine from Tea (Srction 341).—Boil 
gently 10 grams of tea with 500 cc. of water for 15 minutes. 
Filter through a folded filter, and precipitate the tannin by 
adding, drop by drop, to the hot filtrate a 10 per cent solution 
of lead acetate. When a precipitate is no longer formed, filter 
the solution again, and evaporate it toabout 75 cc. If a precipi- 
tate has separated during the evaporation, filter again. Cool the 
solution, and extract it with 30 cc. of chloroform. Separate the 
chloroform and filter it through a dry paper. Set the solution 
aside to evaporate spontaneously. Observe the appearance of 
the crystals. Apply the murexide test to a few of the crystals. 
(See experiment 161d above.) Sublime the rest in watch-glasses. 
(See §35, page 23.) Taste a little of the sublimed caffeine. 


CHAPTER XV 
AROMATIC HYDROCARBONS 


163. Preparation of Benzene from Benzoic Acid (Srcrion 
350).—In a 6-inch evaporating dish place 10 grams of sodium 
hydroxide and 25 cc. of water. Heat over a free flame and stir 
until the sodium hydroxide dissolves; then stir in gradually 
12 grams of benzoic acid. Evaporate to dryness over a free flame, 
which is kept constantly in motion; this will take about 10 
minutes. Grind the mixture of sodium benzoate and sodium 
hydroxide in a mortar, and transfer it to an 8-inch test-tube. 
Clamp the test-tube in an inclined position so that the mouth 
of the tube is slightly lower than the other end; this will prevent 
any water given off during the heating from running back into 
the tube and cracking it. Connect the tube with a condenser 
and receiver, and heat with a free flame kept constantly moving, 
until no more liquid distils over. Measure the volume of the 
benzene and calculate the number of grams and the percentage 
yield obtained. Separate the benzene from the water, dry it 
with calcium chloride, and distil, noting the temperature. 

Benzene melts at 5.4°, boils at 80.4°, and has the specific 
gravity 0.8736 ee . The yield should be about 6 grams. 


Notr.—By converting the benzoic acid into sodium benzoate in the pres- 
ence of an excess of sodium hydroxide, an intimate mixture of the two sub- 
stances is obtained. In this condition the compounds enter into reaction 
more readily and at a lower temperature than does a mixture of the acid 
and soda-lime; such mixtures are commonly used in the preparation of 
hydrocarbons from acids. 

The benzene prepared in this way contains a small amount of diphenyl, 
which may be isolated from the residue left after the distillation of the hydro- 
carbon. The residue on crystallization from alcohol yields crystals of di- 
phenyl, which after two sublimations melt at 71°. 


164. Properties of Benzene (SrcTion 353).—(a) Test for 
thiophene in commercial benzene (SecTION 554).—To a few drops 
of sulphuric acid add a crystal of isatin, about 5 cc. of crude 
benzene, and shake. 

128 


AROMATIC HYDROCARBONS 129 


(b) Test for carbon disulphide in benzene.—Add to about 10 ce. 
of crude benzene 2 drops of phenylhydrazine and set aside for 
some time. If carbon disulphide is present, a crystalline pre- 
cipitate of the formula (CsH;NH.NHe.)2.CS. will separate. If 
crude benzene is not available add 1 drop of carbon disulphide 
to 10 cc. of benzene, and test this mixture. 

(c) Melting-point of benzene (Section 7).—Place about 50 ce. 
of benzene in a flask, insert a thermometer so that the bulb is 
covered, and place in a freezing mixture of ice and salt. When 
the benzene has become solid, remove the flask, and allow the 
mixture to melt partly. Note the temperature when about. 
one-fourth of the benzene is liquid. Pour off the liquid, melt 
the benzene, and place the flask again in the freezing mixture, 
and let it stay until the benzene is solid. Remove the flask and 
determine the melting-point as before. Repeat until the melting- 
point remains constant. Pure benzene melts at 5.4°. 

(d) Inflammability of benzene-—Burn a few drops of benzene 
in an evaporating dish. Is much soot formed? 

(e) Benzene and sulphuric acid.—Shake 2 cc. of benzene with 
about 5 ec. of pure concentrated sulphuric acid. Is the hydro- 
carbon soluble? If the benzene is pure it will not markedly 
color the acid. } 

Shake together about 2 cc. of benzene and 5 cc. of fuming 
sulphuric acid (sp. gr. 1.89 at 20°) as long as heat is developed. 
Does the hydrocarbon dissolve? (Hq.) Pour the mixture 
slowly into a test-tube two-thirds full of ice. Does any insoluble 
substance separate? : 

In order to compare the behavior of aromatic hydrocarbons 
with that of the paraffins, repeat the above experiment using 
petroleum ether or gasoline in place of benzene. 

(f) Benzene and nitric acd —Caution.—As the reaction may 
become violent the mouth of the tube should be held away from 
the experimenter. Repeat experiment (e) above with both ben- 
zene and petroleum ether or gasoline, using fuming nitric acid 
(sp. gr. 1.48) in place of fuming sulphuric acid. When this test 
is applied to unknown substances, very small quantities should 
be used at first, since fuming nitric acid reacts with certain sub- 
stances with explosive violence. 


(g) Test for a double bond in benzene-—Apply the test with a 
: . 


130 EXPERIMENTAL ORGANIC CHEMISTRY 


solution of potassium permanganate. (See experiment 72d, page 
50.) 

(h) Benzene and bromine.—Add to about 10 cc. of benzene 
1 cc. of a solution of bromine in carbon tetrachloride. Divide 
the solution into two parts; place one in direct sunlight and the 
other in the dark in your desk. Observe the two tubes after a 
few minutes. Compare the results with those obtained with 
gasoline (experiment. 70c, page 47) and with amylene (experi- 
ment 74a, page 50). 

Hoop.—Mix 5 cc. of benzene with 2 cc. of bromine. Add a 
small tack or clean piece of iron filings to the mixture. From 
time to time shake the mixture and breathe across the mouth of 
the tube. (Hq.) Let the mixture stand under the hood until 
the next exercise and then pour it into water. Is the liquid 
heavier than water? Explain. 

Notrs.—(d) When aromatic compounds burn they produce a large 
amount of soot. Soot is also formed. when unsaturated compounds and 
paraffin derivatives which contain alkyl radicals with four or more carbon 
atoms are burned. The simpler paraffin derivatives do not produce soot 
on burning. The behavior of an unknown substance on ignition is fre- 
quently determined as a preliminary test in its identification. The test is 
best made by putting some of the liquid or solid on a small roll of copper 
gauze, to which a piece of wire is attached to serve as a handle. 

(e and f) The determination of the behavior of substances with sulphuric 
acid and with nitric acid is a valuable aid in their identification. Aromatic 
compounds yield, in general, soluble sulphonic acids with fuming sulphuric 
acid, and insoluble or difficultly soluble nitro-compounds with fuming 
nitric acid. 

(g) The unsaturation of benzene and other aromatic hydrocarbons is of 
quite a different kind from that of ethylene. Aromatic hydrocarbons do not 
readily react with potassium permanganate in the cold. 


165. Preparation of Ethylbenzene: Fittig Synthesis (Sxc- 
TI0N 347).—(a) In a round-bottomed one-half liter flask, which 
is placed in a vessel containing cold water, put 200 cc. of ether 
dried over sodium (see experiment 95b, page 70) and 27 grams © 
of sodium in the form of a wire or thin shavings. Connect the 
flask by means of a tightly fitteng stopper with a reflux condenser 
through which water is passing. In order to guard against any 
water entering the flask, wrap the stopper and the neck of the © 
flask with a towel. Caution.—Read §41, page 27, carefully. 
When hydrogen is no longer evolved, add through the condenser 


AROMATIC HYDROCARBONS 131 


a mixture of 60 grams of brombenzene and 60 grams of ethyl 
bromide. At the end of about an hour turn off the water from 
the condenser, and let the reaction proceed for at least over night. 
Connect the flask with a condenser and receiver, and distil off 
the ether on a water-bath. Distil the residue directly with a 
large smoky flame, which is kept constantly in motion, as long 
as any liquid passes over. Fractionate (see §23, page 12) the 
product twice, and keep the fraction boiling at 133°-137°. 
Calculate the percentage yield obtained from the brombenzene 
used. Add about 50 cc. of alcohol to the flask containing the 
excess of sodium, and let the mixture stand at least one-half hour. 

Ethylbenzene boils at 135°, and has the specific gravity 0.883 
at 0°. The yield in the preparation should be 25 to 28 grams. 

(b) Ethylbenzene may be considered as a substitution-product 
of ethane and of benzene. Determine whether the hydrocarbon 
shows the characteristic properties of a paraffin or an aromatic 
hydrocarbon. State in your notes what tests were applied and 
the results in each case. 


Notr.—(a) In the preparation of hydrocarbons by the Fittig synthesis 
the halides used are often diluted with ether in order to moderate the reac- 
tion; the volume of ether used ordinarily is twice that of the halogen com- 
pounds. Benzene and petroleum ether are also used as diluents, especially 
in the case of very active substances, when it is desired to have the reaction 
take place very slowly. When reaction takes place sluggishly, the mixture 
without diluents can be heated on a water-bath or in an oil-bath. The 
reaction between halides and sodium is catalyzed by a few drops of ethyl 
acetate or methyl cyanide. 

The rates at which the halides react with sodium are different, and, conse- 
quently, an excess of the more reactive halide is used when a hydrocarbon 
containing two radicals is prepared. In the preparation of ethylbenzene 
the quantity of ethyl bromide required theoretically for 60 grams of brom- 
benzene is 41 grams; it has been found that a better yield is obtained if 60 
grams of ethyl bromide are used. An excess of sodium is also used, as the 
metal becomes coated with sodium bromide, and thus is prevented from fur- 
ther action. The amount of sodium equivalent to 60 grams of brom- 
benzene and 60 grams of ethyl bromide is 21.5 grams; 27 grams of the metal 
are used. 

If all the substances used have not been carefully dried, the hydrogen 
formed as the result of the reaction between sodium and water reduces 
a part of the halides to hydrocarbons. 

In the preparation of hydrocarbons containing two different radicals, the 
product obtained is usually a mixture; in addition to ethylbenzene, some 
diphenyl and butane are formed in the preparation described above, 


132 EXPERIMENTAL ORGANIC CHEMISTRY 


166. Preparation of Diphenylmethane (Section 358).—As a 
large amount of hydrochloric acid is formed in the preparation 
the apparatus should be set up under a hood. In a 500 ce. flask 
provided with a reflux condenser, place 120 grams of benzene 
and an aluminium-mercury couple which is prepared as follows: 
Cut up 2 grams of aluminium foil into strips about 1 inch by 
0.5 inch and allow them to stay in a solution of mercuric chloride, 
made by dissolving 1 gram of the salt in 200 cc. of water, for 
8 to 10 minutes; a film of mercury is deposited on the aluminium. 
Wash the couple thoroughly with water, then with alcohol, ether, 
and finally with benzene. Into the upper end of the condenser 
place a separatory funnel containing 60 grams of benzyl] chloride; 
allow the chloride to drop very slowly into the flask. At the 
end of anhour heat the flask on a water-bath forabout 15 minutes. 
Pour the contents of the flask into an equal volume of water, 
which contains a little sodium hydroxide, shake, separate the 
benzene solution, and extract the aqueous layer once with a 
little benzene. Combine the benzene solutions, and dry them 
with calcium chloride. Pour off the solution into a distilling 
flask, and distil, using a condenser, until the temperature of the 
vapor reaches 150°. Remove the condenser, attach a short air 
condenser, distil, and collect the fraction which boils at 250°-300°. 
Redistil and collect the portion boiling at 255°-265°. Record 
the weight obtained, and calculate the percentage yield from 
the benzyl chloride. The yield should be about 35 grams. 

Diphenylmethane melts at 26° and boils at 262°. 


Notr.—In the preparation of certain compounds by condensation as the 
result of the elimination of chlorine and hydrogen, an aluminium-mercury 
couple gives better results than aluminium chloride. It is probable that a 
little aluminium chloride is first formed by the action of the metal on the 
organic halogen compound; the presence of mercury makes the aluminium 
more active. 


167. Oxidation of Diphenylmethane to Benzophenone (Sxc- 
TIONS 358, 487).—In the identification of organic substances 
they are frequently oxidized and the products isolated. The 
following procedure is an example of one commonly used. Dis- 
solve 5 grams of diphenylmethane in 10 ce. of glacial acetic acid 
and add a solution of crystalline chromic anhydride prepared by 
dissolving 4.5 grams of the anhydride in 5 ec. of water, and 


AROMATIC HYDROCARBONS 133 


adding 30 cc. of glacial acetic acid. Let the mixture stand for 
half an hour, and then warm for an hour on the steam-bath. 
Pour the product into 100 cc. of water, filter off the oil through 
a moist filter paper, dissolve it in 20 cc. of hot alcohol, and add 
cold water until the solution clouds. Set aside to crystallize. 

If an oil separates, rub it against the side of the beaker with 
a glass rod. A form of benzophenone which crystallizes with 
difficulty, is produced as the result of the oxidation of diphenyl- 
methane. If a sample of benzophenone is available a trace can 
be used to seed the oil if it does not crystallize when rubbed sharply 
against the beaker. Determine the melting-point of the crys- ~ 
tals. Benzophenone melts at 48°. : 


Notr.—In oxidizing compounds with chromic anhydride, a slight excess 
is used over that required for the oxidation. Two molecules of the anhy- 
dride furnish three atoms of oxygen. If the compound which is insoluble in 
water is to be oxidized, acetic acid is often used as a solvent. As chronic 
anhydride is difficultly soluble in glacial acetic acid, it is first dissolved in a 
little water and acetic acid added to the solution. Oxidation takes place 
more readily in the presence of a small amount of sulphuric acid, which is 
often used as a catalytic agent. 


168. Formation of Hexaphenylethane (Section 362).—In a 
test-tube put about 20 cc. of ethyl acetate or ether, 1 gram of 
triphenylchlormethane and 5 grams of finely granulated zinc. 
Close the tube with a tightly fitting cork, and shake frequently 
during 10 minutes. Dissolve a little iodine in ethyl acetate. 
Filter off the solution from the zine rapidly through a fluted 
filter-paper into two test-tubes; to one add the iodine solution 
‘drop by drop. (£gq.) Shake the other solution in contact with 
air, (Hq.) set the tube aside, and examine it in a few minutes. 


169. Properties of Naphthalene (Sections 369-371).—(a) 
Solubility of naphthalene-—Test the solubility of naphthalene in 
hot and in cold water, alcohol, and ether. 

(b) Naphthalene and bromine.-—Add bromine, drop by drop, 
to a few crystals of naphthalene. Compare the ease of substitu- 
tion in the case of this hydrocarbon with that of benzene. 

(c) Compound of naphthalene and picric acid.—CauTION.— 
Picric acid stains the hands; it should be handled carefully. 
Dissolve 0.1 gram of the hydrocarbon and 0.2 gram of picric acid 
in 5 cc. of boiling alcohol. Allow the solution to cool spontane- 


134 EXPERIMENTAL ORGANIC CHEMISTRY 


ously, and collect the yellow needles on a filter by suction (see 
§42, page 28) and wash them three times with cold alcohol, using 
1 cc. of alcohol each time. Dry the crystals on a porous tile for 
half an hour in the air, and then determine their melting-point. 
The compound of naphthalene and picric acid has the formula 
CioHs.CgH2(NOz)30H; it melts at 150.5°. 


Notr.—(b) Naphthalene and bromine react readily without the presence 
of a halogen carrier. The reaction can be used to prepare anhydrous hydro- 
gen bromide. 

(c) Picric acid, which is trinitrophenol, forms crystalline addition-prod- 
ucts with a number of organic compounds; these are frequently made as an 
aid in the identification of certain hydrocarbons. (See anthracene, SECTION 
372.) 


CHAPTER XVI 
NITRO COMPOUNDS AND SULPHONIC ACIDS 


170. Preparation of Nitrobenzene (Srctions 383, 385).—To 
80 cc. of concentrated sulphuric acid, contained in a one-half 
liter flask, add 70 cc. of concentrated nitric acid cautiously 
with shaking. Keep the mixture cool by placing the flask in 
cold water. To the cold mixture of acids add slowly and with 
vigorous shaking 50 grams of benzene from a small flask in por- 
tions of about 2 cc. The addition should take about one-half 
hour. From time to time test the temperature of the mixture 
which should be kept warm (40°—50°). If the temperature rises 
above 50°, place the flask in cold water. When all the benzene 
has been added, connect the flask with a reflux air-condenser and 
place it in a water-bath the temperature of which is about 60°. 
Shake the flask vigorously about every 5 minutes. At the end 
of an hour cool the flask in running water, pour the contents into 
a separatory funnel, and separate the upper layer of nitrobenzene 
from the acids. Wash with about 100 cc. of water. As nitro- 
benzene is heavier than water the lower layer is separated this 
time and shaken vigorously with a dilute solution of sodium 
hydroxide until the aqueous layer shows an alkaline reaction. 
The nitrobenzene is finally washed again with water, tested for 
free acid, which should not be present, separated, and warmed 
on the steam-bath with about 10 grams of anhydrous calcium 
chloride until the turbid liquid has become clear and no drops 
of water are visible. Decant or filter the liquid into a distilling 
flask, and distil using an air condenser. Reject the first part of 
the distillate which contains benzene and is apt to be cloudy 
_ due to the presence of a trace of water, and collect what distils 
at 204°-208°. Calculate the percentage yield obtained from the 
benzene. 

Nitrobenzene boils at 207° (uncorrected), melts at 3°, and has 
the specific gravity 1.204 at , The yield should be about 


60-70 grams. 
135 


136 EXPERIMENTAL ORGANIC CHEMISTRY 


Nots.—A low yield of nitrobenzene may be the result of one of the fol- 
lowing causes: Either the nitration was effected at too low a temperature and 
a quantity of benzene is recovered in the final distillation, or the tempera- 
ture of the mixture reaches too high a point and a large amount of dinitro- 
benzene is formed. In the latter case there will be an appreciable residue 
in the flask when the temperature reaches 207° in the final distillation. This 
result is apt to occur if the benzene is added too rapidly at first, and the mix- 
ture of acid kept at too low a temperature; little nitration occurs, and when 
the mixture is heated in the water-bath, the reaction takes place rapidly, 
and the heat generated causes the temperature to rise above 60°, with the 
result that dinitrobenzene is formed. The effect on the result of the tem- 
perature at which nitration is carried out is marked, as can be seen by com- 
paring with the above preparation that of dinitrobenzene described below. 

It is necessary to wash the nitrobenzene free from nitric acid. If this is 
not done, the acid which remains dissolved in the nitrobenzene will react 
further with it when the product is distilled. Brown vapors of oxides of 
nitrogen will be given off, dinitrobenzene will be formed, and an explosion 
may occur. The residue of dinitrobenzene should not be distilled; it is apt 
to decompose violently when the flask is nearly empty. It may be dissolved 
out of the flask and crystallized from alcohol. 


171. Properties of Nitrobenzene (Srctions 384, 391.)—(a) 
Solubility of nitrobenzene-—Describe the odor of nitrobenzene. 
Determine whether nitrobenzene is soluble in alcohol, ether, © 
benzene, dilute hydrochloric acid, and a solution of sodium 
hydroxide. Mix about 2 cc. of nitrobenzene with 5 cc. of con- 
centrated sulphuric acid and pour the mixture into water. How 
could you most readily separate into its constituents a mixture 
of benzene and nitrobenzene? 

(b) Reduction of nitrobenzene to aniline.—Place 2 cc. of nitro- 
benzene and about 3 grams of granulated tin in an 8-inch test- 
tube, and add with constant shaking, in portions of 1 cc., 5 cc. 
of concentrated hydrochloric acid. The acid should be added 
at such a rate that the tube becomes hot, but care should be 
taken to avoid a violent reaction. Do not add the next portion 
of acid until the solution begins to cool. Finally, boil the solu- 
tion for about 3 minutes, shaking the tube constantly. Cool 
under running water and add a strong solution of sodium hy- 
droxide (1:2) until the precipitate first formed has largely dis- 
solved (about 20 cc.). Remove with a pipette a few of the oily 
drops which separate. Put 1 drop of the oil on a watch-glass 
and place near it a drop of concentrated hydrochloric acid; 


NITRO COMPOUNDS AND SULPHONIC ACIDS 137 


bring the drops together by touching them with a glass rod. 
(Hq.) Aniline hydrochloride, CsH;sNH2.HCl, is formed as a 
crystalline solid. Shake up a few drops of the aniline with 2 cc. 
of water and add a few drops of bromine water. Tribromaniline, 
Br3CsH2N Hg, is precipitated. 

(c) Reduction of nitrobenzene to phenylhydroxylamine (Section 
424).—Dissolve 3 drops of nitrobenzene in 2 cc. of water and 
2 ce. of alcohol, and add about 6 drops of a 10 per cent solution 
of calcium chloride and a pinch of zine dust. Heat to boiling 
for one-half minute and filter. Add to the filtrate a strongly 
ammoniacal solution of silver nitrate. The phenylhydroxyl- 
amine, CsH;NHOH, formed as the result of the reaction reduces 
the silver salt to metallic silver. 


Notrrs.—(a) Many nitro compounds are insoluble in sodium hydroxide 
but impart a marked color to the solution of the alkali. Concentrated sul- 
phuric acid is a valuable reagent to separate many nitro compounds from 
substances which are insoluble in the acid. The change in appearance of 
the nitrobenzene after solution and precipitation is due to the fact that when 
a solution of an oil insoluble in water is poured into water, the oil separates 
in minute globules which cause a milky appearance. 

(b) The reduction of nitro compounds to amines, which are soluble in 
dilute acids, is a reaction of importance in their identification. It should 
be noticed, however, that substances other than nitro compounds can be 
reduced to amines. Among these are hydroxylamines, and azo, hydrazo 
and azoxy compounds (Suctions 425, 426). The test is, nevertheless, of 
value in the identification of nitro compounds. 

(c) Nitro compounds are reduced in neutral solution to hydroxylamine 
derivatives; the reaction takes place more readily in the presence of a little 
calcium chloride. The hydroxylamines reduce an ammoniacal solution of 
silver nitrate. Nitroso, azo, and azoxy compounds behave in a similar 
manner. 


172. Preparation of m-Dinitrobenzene (Sxcrion 386).—To 
5 grams of benzene contained in a 100 cc. flask, fitted with a 
cork and a piece of glass tubing about 2 feet long to serve as a 
reflux condenser, add slowly in small portions, shaking the flask 
constantly, a cooled mixture of 18 cc. of concentrated nitric acid 
and 36 cc. of concentrated sulphuric acid. The acid should be 
added at first in portions of about 1 cc.; about 10 minutes are re- 
quired for the addition of the mixture. After the main reaction 
has ceased, remove the condenser and boil the mixture gently over 
a free flame for 5 minutes. Cool the contents of the flask to 


138 EXPERIMENTAL ORGANIC CHEMISTRY 


about 80° and pour the product slowly with stirring into about 
200 cc. of water. Filter by suction, and wash twice with water. 
Dissolve the dinitrobenzene in 40 cc. of hot alcohol and set 
aside to crystallize. Filter off the crystals by suction and wash 
with 10 ce. of cold alcohol. Dry the crystals on a porous plate, 
and determine their melting-point. By adding 10 cc. of water 
to the filtrate a small additional amount of dinitrobenzene can 
be obtained. Calculate the percentage yield. 

m-Dinitrobenzene crystallizes in colorless, odorless needles, 
which melt at 90°, and boil at 297°. It is readily soluble in hot 
alcohol; it dissolves in about 28 parts of alcohol at 20°. The 
yield in the preparation should be about 9 grams. 


Notrre.—Small quantities of benzene and other hydrocarbons can be readily 
identified by converting them into solid nitro derivatives the melting-points 
of which can be determined. As little as 2 or 3 drops of benzene is sufficient 
for the identification of the hydrocarbon in this way. In working with such 
asmall quantity proceed asfollows: Mix 3 drops of benzene and 1 cc. each 
of concentrated sulphuric acid and concentrated nitric acid. Boil the mix- 
ture for one-half minute. Cool, and pour slowly into 10 cc. of water. Shake, 
filter by suction ($42, page 28), and wash with water. Dissolve in a boiling 
mixture of 4 cc. of water and 4 cc. of alcohol. Set aside to crystallize, filter, 
wash with 5 cc. of cold 50 per cent alcohol, and dry on a porous plate. The 
compound prepared in this way melts at 89°-89.5°. 


SULPHONIC ACIDS 


173. Preparation of Sodium Benzenesulphonate (SrcTIon 
392).—In a 250 ce. flask place 50 grams of fuming sulphuric acid 
which contains 8 to 10 per cent of sulphur trioxide (sp. gr. 1.90), 
connect the flask with a reflux condenser, and add, drop by drop, 
from a separatory funnel suspended in the condenser, 20 grams 
of benzene. During the addition of the benzene, which should 
take from 10 to 15 minutes, the flask should be shaken vigorously 
every minute or two. If all the benzene does not dissolve after 
continuous shaking for a few minutes, heat the mixture on a 
water-bath until solution is complete. 

The sulphonic acid formed can be separated in the form of a 
salt by either of the methods described below. In the first 
method (a), which in the case of benzenesulphonie acid is simpler, 
advantage is taken of the fact that sodium benzenesulphonate 


NITRO COMPOUNDS AND SULPHONIC ACIDS 139 


is insoluble in a solution of sodium chloride. The second method 
(b) is the one commonly used to isolate sulphonic acids. It is 
based on the fact that the calcium salts of sulphonic acids are 
soluble in water, whereas calcium sulphate is very difficultly 
soluble. In certain cases it is advisable to prepare the barium 
salts. 

(a) Dissolve 65 grams of sodium chloride in 250 ce. of water, 
and filter the solution if necessary. Measure off 200 cc. of the 
solution, and reserve the rest for washing the crystals of sodium 
benzenesulphonate. Pour into 200 cc. of the salt solution, 
slowly and with stirring, the mixture of benzenesulphonic acid 
and sulphuric acid. Filter off from the warm solution the di- 
phenylsulphone, (CeHs)2SO2, which separates, and cool the - 
filtrate in cold water, using ice if necessary. If crystals do not 
separate, scratch the side of the vessel containing the solution 
with a glass rod. Let the crystals stand with the mother-liquor 
for about 15 minutes to insure the complete separation of the 
salt. Filter by suction, and drain off as much of the liquid as 
possible by pressing the solid down firmly with a spatula. Dis- 
connect the filter-flask from the pump, and cover the salt with a 
part of the sodium chloride solution which was reserved for this 
purpose. When the liquid has penetrated into the solid, remove 
it by the aid of the pump; repeat the washing with more of the 
salt solution. Draw off as much of the liquid as possible, and 
transfer the sodium benzenesulphonate to a porous plate to dry. 
The compound prepared in this way contains about 0.5 per cent 
of sodium chloride. Weigh the product and calculate the yield. 
About 30 grams of sodium benzenesulphonate should be 
obtained. 

(b) Pour the mixture of sulphuric acid and benzenesulphonic 
acid into 500 cc. of water in a large evaporating dish, and heat 
it to boiling. Add precipitated calcium carbonate, which has 
been rubbed to a thick paste with water, until the solution no 
longer shows an acid reaction. Filter through a cotton cloth 
filter to separate most of the calcium sulphate, and wash the 
precipitate with hot water. If a small amount of solid passes 
through the filter the solution need not be refiltered, as the 
precipitate will be removed in a later filtration. EEvaporate the 
solution to about one-half its volume, and add just enough of a 


140 EXPERIMENTAL ORGANIC CHEMISTRY 


solution of potassium carbonate to precipitate the calcium and 
convert the salt into potassium benzenesulphonate. If it is 
difficult to determine when the calcium has just been precipitated, 
filter off a few cubic centimeters of the solution from time to time, 
and add to the filtrate a drop of the solution of potassium car- 
bonate. An excess of potassium carbonate should be avoided, 
for a sample of pure potassium benzenesulphonate is desired. 
Filter off the calcium carbonate, wash it with a little hot water, © 
evaporate the solution to crystallization, and let it cool. Filter 
off the crystals and dry them on a porous plate. The filtrate 
on evaporation will yield a further quantity of the salt. Calcu- 
late the percentage yield obtained. 

Potassium benzenesulphonate crystallizes in lustrous plates, 
which effloresce in the air. The salt is very soluble in water, and 
melts above 300° with decomposition. 


Norre.—(b) The free sulphonic acid can be obtained from the calcium 
salt by adding to its solution just enough sulphuric acid to precipitate the 
calcium as sulphate, evaporating the solution to a small volume, and placing 
it in a desiccator to evaporate over sulphuric acid. In the preparation of 
free sulphonic acids in this way it is better to prepare the barium salt, 
as barium sulphate is less soluble in water than calcium sulphate, and the 
free acid is not contaminated with a small amount of sulphate. 


174. Identification of a Sulphonic Acid by Conversion into 
a Phenol (Section 399).—Melt about 1 gram of sodium hydroxide 
in a small iron or porcelain crucible, and add to the fused mass 
about 0.5 gram of sodium benzenesulphonate. Keep the mixture 
just above its melting-point, and do not let it char. Stir occa- 
sionally during 5 minutes. Cool, dissolve in water, acidify 
with dilute hydrochloric acid, and note the odor produced. 
Filter and add bromine water, drop by drop. Write equations 
for all the reactions involved in the test. | 


175. Preparation of Benzenesulphonyl Chloride (SrcTion 
395).—Convert all of the salt of benzenesulphonic acid obtained 
in experiment 173 above into benzenesulphonyl chloride as 
follows: Hoop. Place the dry salt in a flask and add phos- 
phorus pentachloride, which should be weighed in the hood, in 
the proportion of 3 parts by weight of the salt to 4 parts 
by weight of the chloride. Heat the mixture on the steam-bath, 


NITRO COMPOUNDS AND SULPHONIC ACIDS 141 


with occasional shaking, for half an hour. Cool, and add to the 
liquid about ten times its volume of ice-water. Shake about 
every 10 minutes in order to facilitate the reaction of the 
phosphorus oxychloride present with water. At the end of an 
hour pour off the water and wash the oil twice with water 
by decantation. Separate the benzenesulphonyl chloride and 
calculate the percentage yield. . 

The chloride can be used without further purification for the 
experiments given below. If it is desired to preserve the chloride 
- for future use (see experiment 186, page 152), it should be taken 
up in ether, dried over calcium chloride and distilled under 
reduced pressure (§24, page 14) after the ether has been 
removed. 

Benzenesulphonyl] chloride is a colorless liquid which distils 
at 246°-247° with decomposition, and undecomposed at 120° 
under a pressure of 10 mm. It melts at 14.5°. 


176. Preparation of Benzenesulphonamide (Srction 396).— 
Put into a test-tube about 1 cc. of benzenesulphonyl chloride 
and add about 5 cc. of strong ammonia. Shake until a solid is 
formed and the odor of the chloride has disappeared. Pour 
off the liquid and wash twice with water by decantation. Add 
about 20 cc. of water; heat to boiling until the substance has 
dissolved. Filter, if necessary, and set the solution aside to 
crystallize. When cold, filter by suction, wash with cold water, 
and dry the amide for half an hour on a porous plate. Determine 
the melting-point of the amide. If the crystals do not melt 
sharply, recrystallize them from hot water. 

Benzenesulphonamide crystallizes from hot water in needles, 
which melt at 156°. 


Notrre.—Sulphonamides are frequently made in the identification of sul- 
phonic acids or their salts. The preparation can be carried out with small 
quantities in a few minutes. Proceed as follows: Warm together in a test- 
tube on a steam-bath about 0.5 gram of the salt with an equal volume of 
phosphorus pentachloride, until the mixture liquefies. Cool, pour 5 cc. of 
water into the tube, warm gently, and shake for about 1minute. Pour off 
the liquid and wash twice by decantation with 5 cc. of cold water. Add 
5 ec. of ammonia and proceed as described in the experiment above. 


177. Preparation of p-Toluenesulphonic Acid (Srction 397).— 
To 25 grams of toluene in a 200 cc. flask add 25 cc. of pure con- 


142 EXPERIMENTAL ORGANIC CHEMISTRY 


centrated sulphuric acid, and place on the steam-bath. Allow 
the mixture to stand until the toluene has dissolved. This will 
require about 2 hours if the flask is shaken once in a while. Let 
the solution cool; before it solidifies pour it, with stirring, into 
100 ec. of pure concentrated hydrochloric acid. Heat the mix- 
ture on the steam-bath until the solid dissolves. Set aside to 
crystallize. Filter by suction, and wash the crystals with con- 
centrated hydrochloric acid. Press the crystals to remove as 
much of the mother-liquor as possible and dry them on a porous 
plate. Weigh the toluenesulphonic acid and calculate the 
percentage yield from the toluene used. 

p-Toluenesulphonic acid crystallizes from water, in which it is 
very soluble, in long colorless needles. It is less soluble in con- 
centrated hydrochloric acid. It melts at 104°-105°. The yield 
should be about 25 grams. The amide can be prepared by the 
method described in experiment 176; it melts at 1386°-137°. 


CHAPTER XVII 
HALOGEN DERIVATIVES OF AROMATIC HYDROCARBONS 


178. Preparation of Brombenzene (Srction 403).—To 50 
grams of benzene in a 200 cc. flask add 35 ec. (105 grams) of 
bromine. Fit the flask with a cork stopper through which passes 
a glass tube, bent twice at right angles. The longer arm of the 
tube which passes through the cork should be about 2 feet long. 
Place below the end of the shorter arm a flask containing 100 ce. 
of water to absorb the hydrobromic acid formed in the reaction; 
the end of the tube should be just above the surface of the water. 
Put the flask containing the benzene and bromine in a pail or 
large beaker containing ice-water, and add to the flask two 
clean iron tacks or nails. Allow the reaction to proceed until the 
next laboratory exercise. Wash the product with water, and 
with a little sodium hydroxide if necessary, until any excess of 
bromine: has been removed. Place the liquid in a separatory 
_ funnel, separate it, and dry it with anhydrous calcium chloride. 
Fractionate three times, collecting the following fractions: 
up to 120°, 120°-150°, 150°-160°, 160°-200°. The fraction 
boiling at 150°—160° is practically pure brombenzene. Calculate 
the molecular proportions in which the reacting-substances were 
used in the preparation and the percentage yield obtained. 
Determine the specific gravity of the brombenzene (§56, page 
37). 

The residue boiling above 200° contains p-dibrombenzene. 
It may be poured while still hot onto a watch-glass, and crystal- 
lized from alcohol. eee directions under the preparation of 
dibrombenzene.) 

Put the hydrobromic acid collected as a by-product in the 
reaction into the bottle provided for hydrobromic acid residues. 
This preparation yields a large amount of hydrobromic acid, as 
one-half of the bromine used is converted into the acid. On 
distillation the aqueous solution yields an acid than can be used 
conveniently for the preparation of alkyl halides. 

143 


144 EXPERIMENTAL ORGANIC CHEMISTRY 


Brombenzene boils at 156°, and has the specific gravity 1.491 
at 20°. The yield in this experiment should be from 60 to 65 
grams. 

Notr.—In order to obtain a good yield of brombenzene, it is advisable to 
keep the mixture of benzene and bromine cold during the reaction. The 
product obtained consists of a mixture of benzene, brombenzene, and dibrom- 
benzene. The effect of the temperature on the reaction is clearly seen by 
comparing the method used in this preparation with that employed to pre- 
pare dibrombenzene. See the experiment below. 

179. Preparation of p-Dibrombenzene (Section 404).—Hoop. 
—To 5 grams of benzene in a small round-bottomed flask add 
10 ce. of bromine. Close the flask with a cork through which 
passes a piece of glass tubing about 3 feet long to serve as a reflux 
condenser. Place the flask in the hood, drop into it a tack or 
piece of clean iron filing, and allow the reaction to proceed 
spontaneously to completion; this usually takes about 30 minutes. 
Then heat the flask cautiously over a free flame for 2 minutes to 
expel most of the excess of bromine. Add about 50 ce. of water 
and heat to boiling, shaking vigorously. Cool until the dibrom- 
benzene solidifies, and decant off the liquid. Repeat the wash- 


ing with hot water twice, adding to the liquid the last time 
about 50 cc. of a solution of sodium hydroxide. Cool and wash 
the crystals once more with cold water, decant off the water, 
add 75 cc. of alcohol and a little bone-black, and heat to boiling. 
Filter the hot solution, and add 20 cc. of water. Set aside to 
crystallize. Separate the crystals and determine their melting- 
point. Calculate the percentage yield obtained. 
p-Dibrombenzene crystallizes in colorless leaflets, which melt at 
89° and boil at 219°. The yield should be about 13 to 14 grams. 


180. Properties of Aromatic Halogen Compounds (SEcTION 
401).—(a) Solubility of halogen compounds.—Determine whether 
brombenzene is soluble in the following: Water, alcohol, ether, 
concentrated sulphuric acid, dilute hydrochloric acid, and a 
solution of sodium hydroxide. 

(b) Inflammability of halogen compounds.—Wrap a strip of 
copper gauze about 1 cm. wide around a piece of wire to serve 
as handle, so that a roll about as thick as a lead pencil is formed. 
Pour a few drops of the liquid or place a few crystals on the gauze 
and place it for an instant in a flame. Remove the gauze and 


. HALOGEN DERIVATIVES 145 


note whether soot is formed by holding the burning substance 
in front of a piece of white paper. Determine whether the 
following substances burn, and whether soot is produced: Ben- 
zene, brombenzene, dibrombenzene, benzyl chloride, ethyl bromide, 
chloroform, carbon tetrachloride. What conclusions can be 
drawn from the experiment? (See the note to experiment 164d, 
page 129.) 

(c) Comparison of the behavior of compounds containing the 
halogen joined directly to the benzene ring with those containing the 
halogen in a side-chain.—Read carefully Sections 401, 402. 
Compounds of the two classes behave differently with an alco- 
holic solution of potassium hydroxide. In order that conclusive 
results may be drawn from the test, it is necessary to have a solu- 
tion of the alkali which is free from halogen. As all samples 
of commercial potassium hydroxide contain potassium chloride, 
prepare a solution by dissolving about 1 gram of the hydroxide 
in 20 cc. of absolute alcohol; filter from the undissolved carbonate 
and chloride and use the clear filtrate for the tests.! Test a 
part of the solution so prepared for a halide as follows: Dilute 
with water, acidify with nitric acid, and add silver nitrate. Add 
3 drops: of benzyl chloride to 5 cc. of the alcoholic potassium 
hydroxide solution, and boil gently for 2 minutes. Dilute with 
water, acidify with pure dilute nitric acid, and add a few drops of 
a solution of silver nitrate. Repeat the experiment, using 
brombenzene. In order not to confuse with silver bromide 
the cloudiness produced when the brombenzene is precipitated 
from the alcoholic solution by the addition of water, add 3 drops 
of brombenzene to 5 ce. of alcohol and dilute with the amount - 
of water used in the test. Compare the appearance of the solu- 
tion with the one which was heated. If the unchanged precipi- 
tated organic halogen compound interferes with the observation 
of the silver halide, it can be removed by shaking the solution 
with ether, and adding the silver nitrate to the clear aqueous 

solution. 


Notre.—(c) In applying this test it is necessary to determine first whether 
the compound contains any free halogen acid, which has been produced as 


1 A solution which can also be used for the test may be prepared by dis- 
solving about 0.5 gram of clean sodium, free from any crust, in 20 cc. of alco- 
hol and adding a few drops of water. 

10 


146 EXPERIMENTAL ORGANIC CHEMISTPRY 


the result of decomposition onstanding. Shake a little of the substance with 
water, and test the aqueous solution with silver nitrate. If a precipitate is 
formed, the halide must be washed with water until the latter gives no test 
for halides. 


181. Preparation and Properties of Triphenylchlormethane 
(Suction 409).—(a) Place in a 500 cc. flask 25 grams of carbon 
tetrachloride, 50 grams of benzene, 100 cc. of carbon disulphide, 
and 30 grams of anhydrous aluminium chloride. It is important 
to avoid exposing the aluminium chloride to the air any longer 
than necessary. Attach to the flask by means of a stopper a 
small drying tube containing anhydrous calcium chloride, and 
leave the flask in the hood for at least 2 days. At the end of 
this time the mixture is poured onto 200 grams of ice, and stirred 
occasionally until the dark-colored addition-product of aluminium 
chloride and triphenylehlormethane has decomposed, and the 
latter salt has dissolved in the carbon disulphide. Separate the 
carbon disulphide, and filter it through a paper over which car- 
bon disulphide has _been poured. Add to the filtrate anhydrous 
calcium chloride, and shake occasionally until the solution is 
clear. Filter the solution through a dry filter-paper into a dis- 
tilling flask. Attach the flask to a water-jacketed condenser, 
and distil off the solvent on a water-bath. Pour the residue into 
a beaker, and when it is cool, add 20 cc. of petroleum ether. 
Allow the mixture to stand for 15 minutes. Filter by suction, 
and wash the triphenylchlormethane with 20 cc. of petroleum 
ether. Let the crystals stand in the air for a few minutes until 
dry. Weigh the product and calculate the percentage oe 
’ from the carbon tetrachloride used. 

Triphenylchlormethane melts at 109°-111°. It can be crys- 
tallized from boiling ligroin, in which it is readily soluble hot 
and difficultly soluble cold. Since triphenylechlormethane is 
decomposed when heated with water, anhydrous solvents should 
be used. The compound can be obtained in a very pure condition 
by recrystallizing it from boiling acetyl chloride. The yield 
in this preparation is about 85 per cent. 

Norr.—If the dark red oil which separates at first in the reaction is decom- 
posed at once by water, benzophenone chloride, (C6Hs5)2CCle, is obtained. 


This red oil, which is a molecular compound of benzophenone chloride and 
aluminium chloride, reacts on standing with more benzene and is converted 


HALOGEN DERIVATIVES 147 


into a substance of the composition (CsHs)s;CCl.AlCls, which is a crystalline 
solid. Water decomposes this addition-product into its constituents. 


(b) Reaction with water.—Powder about 0.1 gram of triphenyl- 
chlormethane and shake it in a test-tube with water. Let the 
mixture stand a few minutes and then test the aqueous solution 
for hydrochloric acid with litmus paper and with silver nitrate. 

(c) Reaction with sulphuric acid—In a small beaker treat 
about 2 grams of triphenylchlormethane with 5 cc. of concen- 
trated sulphuric acid, and shake until solution is complete. Is 
hydrogen chloride given off? Compare the results with those 
obtained with ethyl bromide (experiment 132a, page 98). 
Pour the solution into 50 cc. of water, filter off by suction the 
precipitate of triphenylearbinol, wash with water, and dry it. 
Add a small amount of the carbinol to a little concentrated sul- 
phurie acid on a watch-glass. Grind thoroughly some of the 
carbinol in a mortar with a little concentrated hydrochloric 
acid for about 1 minute. Remove the product with a spatula 
to a porous plate and let it dry. Add the compound to a little 
concentrated sulphuric acid. Write equations for all reactions 
which take place. 

_(d) Reaction with silver nitrate—Dissolve a bit of triphenyl- 
chlormethaneé in a little acetone and add an alcoholic solution 
of silver nitrate. (Hq.) 

(e) Reaction with metals—Repeat experiment 168, page 133. 


CHAPTER XVIII 
AROMATIC AMINES 


182. Preparation of Aniline (Secrion 415).—Provide a 1 liter 
flask with a cork and tubes arranged for distillation with steam 
($28, page 18); the tubes will be needed later in the prepara- 
tion and should be ready for use. Place in the flask 25 grams of 
nitrobenzene and 50 grams of granulated tin, and connect it with 
a reflux air-condenser. Add to the mixture 125 cc. of concen- 
trated hydrochloric acid in the following way: Add about 10 cc. 
of the acid and shake vigorously. If reaction does not take 
place in a minute or two, warm gently until there is an evolution 
of hydrogen and the reaction produces sufficient heat to keep the 
flask warm. When the reaction subsides, add another portion of 
10 cc. of acid, and shake. Continue in this way until about 
one-half the acid has been added. If the reaction becomes too 
vigorous and there is chance of vapor escaping from the flask, 
place the latter in cold water. Care must be taken not to keep 
the flask so cold that the reaction does not proceed rapidly. The 
last half of the acid may be added in portions of about 20 cc. 
When all the acid has been added, heat the flask on a boiling 
water-bath, shaking occasionally, until no drops of nitrobenzene 
can be seen floating on the surface of the liquid. The odor of 
nitrobenzene should also disappear. From 4% to 1 hour is 
required to complete the reaction in this way.! Add to the 
hot solution 50 cc. of water, place the flask in cold water, and 
add a solution of 90 grams of sodium hydroxide in 150 cc. of 
water until most of the precipitate first formed has dissolved and 
the solution shows a strong alkaline reaction. The mixture 
must not be cooled too strongly; it is necessary only to keep it 
from boiling in order to prevent loss of aniline. Distil with 

1Tf the preparation can not be completed in one exercise it is well to stop 
at this point; if the alkali to liberate the aniline is added, and the mixture 
allowed to cool, it is necessary to heat the flask to boiling before the contents 


are distilled with steam. The distillation requires about an hour. 
148 


AROMATIC AMINES 149 


steam. ‘The aniline passes over at first as a colorless oil. As 
the compound is somewhat soluble in water (about 1 part in 30), 
the distillation should be continued after the drops cease to form; 
change the receiver at this point and collect about 100 cc. of the 
solution. Combine the two distillates and saturate the solution 
with sodium chloride, using 20 grams of salt for each 100 cc. of 
solution. Extract twice with ether using about 200 ec. each 
time (§31, page 20). Separate the ether, place it in a bottle, 
and add 3 or 4 sticks of potassium hydroxide. Stopper the 
bottle and let the solution stand over night. Filter the solution 
into a dry flask. The water extracted from the ethereal solution 
forms with the potassium hydroxide a saturated solution of the 
alkali; care should be taken not to allow this to get into the flask. 
Distil off the ether on a water-bath (see §34, page 22). Trans- 
fer the residue to a small dry flask, wash out the first flask with 
a few cubic centimeters of the dry ether which has just been dis- 
tilled off, and add the solution to the aniline. Distil over a free 
flame using an air-condenser, heating cautiously until the small 
amount:of ether has come over, and collect the fraction boiling 
at 180°-184°.. Calculate the percentage yield obtained. 

Aniline boils at 182° (183.7° corrected), and has the specific 
gravity 1.024 at 16°. The yield should be from 85 to 90 per cent. 


183. Properties of Aniline (Sections 411, 415).—(a) Solubility 
of aniline.—Determine whether aniline is soluble in the following: 
water, dilute sodium hydroxide, dilute hydrochloric acid, con- 
centrated sulphuric acid, alcohol, and benzene. 

(b) Salts of aniline—Add 2 cc. of aniline to 5 cc. of water 
and add 1 cc. of concentrated sulphuric acid. Heat to boiling 
and set the solution aside to crystallize. (Hq.) 

Heat together in a small beaker about 5 cc. of aniline, 5 cc. of 
water, and 10 cc. of concentrated hydrochloric acid. When the 
solution is cold, filter off the crystals by suction; do not wash 
them with water in which they are very soluble. Dry the crystals 
in a beaker on the steam-bath. The salt will be needed for the 
following experiments. 

(c) Double salts containing aniline—Make a saturated solu- 
tion of about 1 gram of aniline hydrochloride in a little water. 
To one-half of the solution add a few drops of a solution of plati- 


150 EXPERIMENTAL ORGANIC CHEMISTRY 


num chloride, and to the other a few drops of saturated solution 
of stannous chloride, and cool. (Kgqs.) 

(d) Base-forming property of aniline—Make a saturated aque- 
ous solution of aniline by shaking about 1 cc. of the amine with 
15 cc. of water. Test the clear solution with litmus paper, and — 
add some of it to a solution of aluminium sulphate or chloride. — 
Compare the results with those obtained with methylamine (ex- 
periment 113b, page 86). Explain. 

(e) Hydrolysis of salts of aniline-—Dissolve a little aniline hy- 
drochloride in water and test the solution with litmus paper. Is 
the result in accord with those obtained in (d) above? Explain. 

(f) Reaction of salts of aniline with bases.—Add to a concen- 
trated aqueous solution of aniline hydrochloride a solution of 
sodium hydroxide. (Kq.) 

(g) Aniline and acetyl chloride—Add acetyl chloride, drop 
by drop, to 1 ce. of aniline as long as an evident reaction takes 
place. Add about 15 cc. of water and heat to boiling, filter hot, 
and cool in running water. (Hq.) Filter off the precipitate by 
suction, wash twice with cold water, and dry the crystals on a 
porous plate for half an hour. Determine the melting-point of 
the crystals. Acetanilide melts at 112° Amines are frequently 
identified by converting them into acetyl derivatives. 

(h) Aniline and bromine.-—Add bromine-water, drop by drop, 
to an aqueous solution of aniline until the solution becomes 
yellow. Tribromaniline, which is precipitated, crystallizes from 
alcohol and melts at 116°. 

(2) Aniline and nitrous acid.—Dissolve about 1 ce. of aniline 
in 2 ec. of concentrated hydrochloric acid and 5 ec. of water. 
Cool the solution in running water. Add a cold solution of about 
0.5 gram of sodium nitrite in 5 cc. of water. Shake, and heat 
gently. Observe that a gas is given off, and note the odor of 
the solution. (Kq.) 

(7) Aniline and ferric chloride.—Add to an aqueous solution of 
aniline a few drops of a dilute solution of ferric chloride. 

(k) Aniline and hypochlorites—Add to a dilute aqueous -solu- 
tion of aniline a solution of bleaching powder or of sodium 
hypochlorite. . 

(1) Aniline and potassium bichromate.—Mix on a watch-glass 
a drop of aniline with 38 drops of concentrated sulphuric acid, 


AROMATIC AMINES 151 


and add 2 drops of a solution of potassium bichromate. Note 
the color, and heat on the steam-bath for a few minutes. 

(m) Aniline and methyl iodide—Mix together 3 cc. of aniline 
and 2 cc. of methyl iodide, and let the mixture stand in a stop- 
pered tube until the next exercise. (Hq.) Remove the crystals, 
dry them on a porous plate, and then treat them with a strong 
solution of sodium hydroxide. (Hgq.) Note the odor. Is it like 
that of aniline? 


Notrs:—(a) The solubility of many amines in dilute hydrochloric acid 
serves to distinguish them from other nitrogen compounds.’ Amines which 
contain a number of strongly negative groups are insoluble in the acid. 

(g) Acetyl chloride is a useful reagent to distinguish primary and second- 
ary amines from tertiary amines. Alcohols and phenols also react. with 
acetyl chloride. 

(h) Many amines give a precipitate of an insoluble substitution-product 
when treated with bromine water; certain phenols give a similar reaction. 


184. Properties of Methylaniline (Smctions 412, 420).—(a) 
Methylaniline and acetyl chloride—Add acetyl chloride, drop 
by drop, to about 1 cc. of methylaniline, add water, and heat to 
boiling. Cool. (Hq.) The acetyl derivative formed melts at 
102°. 

(b) Methylaniline and nitrous acid.—Repeat experiment 1832, 
page 150, using methylaniline in place of aniline. Is an oil 
formed? Compare the results in the two experiments. (q.) - 


185. Properties of Dimethylaniline (Srcrions 413, 422).— 
(a) Dimethylaniline and acetyl chloride.—Repeat experiment 184a, . 
page 151, and compare the results obtained when primary, sec- 
ondary, and tertiary amines are treated with acetyl chloride. 

(b) Dimethylaniline and nitrous acid: nitroso-dimethylaniline.— 
Dissolve 5 grams of dimethylaniline in a mixture of 10 cc. of 
concentrated hydrochloric acid and 40 cc. of water. Cool the 
mixture in ice-water, and add, slowly with stirring, a solution of 
3 grams of sodium nitrite in 20 ce. of water. At the end of 15 
minutes filter off the salt by suction, wash with dilute hydro- 
chloric acid, and crystallize a little of it from warm (about 60°) 
dilute hydrochloric acid. Shake up the rest with an excess of a 
solution of sodium hydroxide. Dissolve a little of the precipi- 
tate in ether, filter the solution, and let it evaporate. Boil some 
of the free amine with sodium hydroxide, note the odor of the gas 


152 EXPERIMENTAL ORGANIC CHEMISTRY 


given off, and test it with moist litmus paper. Write equations 
for all the reactions. 


186. Use of Benzenesulphonyl Chloride in Distinguishing the 
Three Types of Amines (Section 395).—Shake together for 2 
or 3 minutes 0.5 cc. of aniline, 50 cc. of a strong aqueous solution 
of sodium hydroxide (1 to 4) and 2 cc. of benzenesulphonyl 
chloride. Warm gently until the odor of the chloride disappears. 
Filter and add hydrochloric acid to the filtrate. (Hqs.) 

Repeat the experiment using methylaniline and then dimethyl- 
aniline. Test the solubility in dilute hydrochloric acid of the 
substances separated in these two cases by filtration. Write 
equations for all reactions, and state clearly how the reagent 
serves to distinguish from one another the three classes of amines. 


Notr.—A few primary amines yield products with benzenesulphonyl 
chloride which do not dissolve in a dilute solution of sodium hydroxide. 
This is due to the fact that a difficultly soluble sodium salt is formed, which 
is partially hydrolyzed. Such compounds are converted into sodium salts 
by strong solutions of the base. 


CHAPTER XIX 
DIAZO COMPOUNDS 


187. Preparation of Phenol from Aniline (Section 429).— 
Prepare some iodo-starch paper for use as an indicator for nitrous 
acid as follows: Grind about 1 gram of starch with a few cubic 
centimeters of water and pour the mixture into 200 cc. of boiling 
water. Cool the solution and dissolve in it a crystal of potassium 
iodide. Insert pieces of filter-paper into the solution, and hang 
them up to dry in a place free from acid vapors. The moist 
paper can be used in the following preparation. 

In a 500 cc. beaker pour 25 cc. of concentrated sulphuric acid 
into 200 cc. of water, and add to the warm solution 20 grams of 
aniline slowly and with vigorous stirring. Cool, and add 100 
grams of ice. Dissolve 16 grams of sodium nitrite in 100 cc. of 
water, and add the solution in small quantities, with stirring, to 
the solution of aniline sulphate, until the amine has been diazo- 
tized. This can be determined by testing the solution for nitrous 
acid, which will be present when the nitrite has been added in 
excess. The amount of nitrite which has been dissolved is a 
slight excess over that required for the reaction. When the larger 
portion of the nitrite has been added, stir vigorously, place a drop 
of the solution on a piece of iodo-starch paper. If free nitrous 
acid is present a blue spot willform. (Kq.) Continue the addi- 
tion of nitrite until the solution, after thorough stirring and stand- 
ing 15 to 20 seconds, produces an immediate blue color with the 
iodo-starch paper. Pour the solution of the diazonium salt into a 
flask, and heat it at 40°-50° ona water-bathfor halfanhour. Distil 
with steam (§28, page 18) and collect about 300 cc. of distillate. 
As long as any phenol distils over the distillate will give a color 
with a solution of ferric chloride. Saturate the solution of phenol 
with sodium chloride, and extract three times with ether, using 100 
ec. each time. Let the ether solution stand over night with about 
one-fifth its volume of anhydrous sodium sulphate. Filter the 
ether, and distil it off from a flask on a water-bath (§34, page 22). 

153 


k 


154 EXPERIMENTAL ORGANIC CHEMISTRY 


Wash the drying agent with some of the recovered ether, and add 
this solution to the flask. Pour the residue into a small flask, 
and distil using an air-condenser. Collect the fraction boiling at 
180°-183°. Calculate the percentage yield. 

Phenol melts at 43°, boils at 183°; it is soluble in about 15 parts 
of water at 16°. The yield in this preparation should be about 
15 grams. 


Norte.—In the preparation of diazonium salts it is advisable to keep the 
reaction-mixture cold during the addition of the nitrite solution, even in the 
case when the resulting salt is to be decomposed by water; in this way the 
formation of by-products is largely avoided. 

A small amount of p-hydroxydiphenyl, Cs>H;.CsH,OH, is formed as the 
result of the condensation of the diazonium salt with some of the phenol 
formed in the reaction. The compound can be obtained by filtering the 
hot solution from which the phenol has been distilled. On cooling, -p-hy- 
droxydipheny] separates out in plates which melt at 164°. 


188. Preparation of Iodobenzene from Aniline (SmcTions 429, 
405).—Mlix together in a beaker 150 cc. of water, 12 cc. of con- 
centrated sulphuric acid, and 10 grams of aniline. Cool the 
solution, and add 100 grams of ice. Diazotize the solution by 


adding a solution of 8 grams of sodium nitrite dissolved in 40 cc. | 


of water in the way described in the above experiment (prepara- 
tion of phenol). Pour the solution of the diazonium salt into a 
liter flask and add a solution of 22 grams of potassium iodide in 
50 ce. of water. Place the flask in a water-bath heated to 70° 
80° until the evolution of nitrogen ceases. Make the solution 
strongly alkaline by adding a solution of sodium hydroxide, and 
distil with steam as long as an oil comes over. It is necessary 
to have the end of the tube through which the steam enters the 
flask pass to the bottom of the latter, so that the steam passes 
through the heavy oil, and keeps it constantly in motion. Sepa- 
rate the iodobenzene, and dry it with calcium chloride. Filter 
it into a small flask and distil, using an air-condenser. Calculate 
the percentage yield. 

Iodobenzene boils at 188° (corrected). The yield should be 
about 20 grams. 


189. Preparation of p-Tolunitrile: Sandmeyer Reaction (Src- 
TION 429).—CavutTion.—In this preparation cuprous cyanide is 
to be used. The compound is made from copper sulphate and 


DIAZO COMPOUNDS 155 


potassium cyanide. As the reaction involves the liberation of 
cyanogen, a very poisonous gas, it should be carried out under 
the hood with a good draught, and care should be taken not to 
breathe any of the gas liberated. Care should be exercised also 
in handling the potassium cyanide. 

Dissolve 50 grams of copper sulphate in 200 cc. of hot water, 
place the solution in a 2 liter flask on a water-bath heated to 
boiling under the hood, and add in small portions a solution of 
55 grams of potassium cyanide dissolved in 100 cc. of water. 
Leave the solution heating on the water-bath, and prepare the 
diazo compound as follows: Add 20 grams of p-toluidine to a 
mixture of 45 cc. of concentrated hydrochloric acid and 100 cc. 
of water, and stir. Place the vessel containing the solution in 
cold water, add 100 grams of ice, and diazotize with a solution of 
16 grams of sodium nitrite in 60 cc. of water, taking precaution 
to avoid an excess of the nitrite solution. (See experiment 187 
above.) Hoop.—Pour the diazo solution into the hot solution 
of cuprous cyanide; add about 10 cc. at a time and shake vigor- 
ously. Avoid running the solution down the side of the flask; 
it should fall directly into the solution of the cyanide. This 
precaution is taken to avoid as much as possible the formation of 
cresol, CH3.CeH.4.OH, as the result of the interaction of the 
diazo compound with water. The addition of the diazo solution 
should take about 15 minutes. Leave the flask on the water- 
bath for about 15 minutes more, and when the evolution of nitro- 
gen ceases, distil with steam under the hood. If the tolunitrile 
solidifies in the condenser, turn off the water in the latter for a 
short time; the steam will warm the water in the condenser, and 
the nitrile will melt. Distil as long as an insoluble substance 
comes over in appreciable amounts. If only a small amount of 
cresol has been formed the nitrile will solidify in the receiver. 
Separate the crystals and let them dry spontaneously on. a 
porous plate. As tolunitrile melts at 38°; the crystals should not 
be put in a warm place. Weigh the crystals, and calculate the 
percentage yield. Save the preparation for a future experiment. 

If much cresol has been formed during the reaction the product 
will not solidify. In this case, extract with a small amount of 
ether, shake the ethereal solution with an equal volume of a solu- 
tion of sodium hydroxide, and dry over calcium chloride. Pour 


156 EXPERIMENTAL ORGANIC CHEMISTRY 


off the solution, distil off the ether, and distil, using an air- 
condenser. 

p-Tolunitrile melts at 38° and boils at 218°. The yield should 
be about 13 grams. 


190. Preparation of Diazoaminobenzene (Srction 430).—Dis- 
solve 10 grams of aniline in a mixture of 100 cc. of water and 20 
ee. of concentrated hydrochloric acid. Add 100 grams of ice. 
When the solution is cold add a solution of 8 grams of sodium 
nitrite in 40 ce. of water. Dissolve 10 grams of aniline in a mix- 
ture of 7 cc. of concentrated hydrochloric acid and 50 ce. of water, 
and add 50 grams of ice. Pour the solutions of aniline hydro- 
chloride slowly with stirring, into the solution of the diazo com- 
pound. (Hg.) Dissolve 25 grams of hydrated sodium acetate in 
50 cc. of water, and add the solution to the mixture. At the 
end of half an hour, add about 300 cc. of water, stir, and filter 
by suction; wash the precipitate with cold water. Press the 
diazoaminobenzene on a porous plate, and let it stand until dry; 
do not heat it. Weigh the product and calculate the percentage 
yield. 

Crystallize a little of the compound from petroleum ether as 
follows: Digest for 2 or 3 minutes 2 grams of the diazoamino- 
benzene with 100 cc. of petroleum ether, filter hot, evaporate to 
about 50 cc.,and set aside the solution to crystallize. 

Diazoaminobenzene crystallizes in yellow plates, which melt 
at 98°; it explodes when heated above its melting-point. It is 
insoluble in water, and is soluble in benzene, ether, and alcohol. 
The yield obtained in the above preparation is about 15 grams. 


Notre.—The sodium acetate is added to interact with the excess of hydro- 
chloric acid present: 


HCl + CH;COONa = NaCl + CH;COOH 


The salt is frequently added to solutions containing strong acids when it 
is desired to bring about a reaction which does not take place in the presence 
of such acids. (See diazoamino compounds, SrectTion 430.) 


191. Preparation of Aminoazobenzene (Srection 431).—Mix 
in a small beaker 10 grams of diazoaminobenzene, 20 grams of 
aniline, and the aniline hydrochloride prepared as follows: Dis- 
solve 5 cc. of aniline in 10 cc. of concentrated hydrochloric acid, 
cool in running water, filter by suction, press on a porous plate. 


DIAZO COMPOUNDS 157 


Allow the salt to dry for about 5 minutes. Heat for 1 hour on 
a water-bath the mixture so that the temperature of the latter is 
between 50° and 60°; stir frequently. Dissolve the product in 
50 cc. of glacial acetic acid, and pour the solution slowly into 
400 ce. of water, stirring vigorously. After about 5 minutes 
filter by suction, wash with water and set aside to dry. 

Convert a part of the aminoazobenzene into the chloride as 
follows: Dissolve 2 grams of the compound in 10 ce. of alcohol 
and pour the solution into a boiling mixture of 20 cc. of concen- 
trated hydrochloric acid and 200 ce. of water. Boil for 10 min- 
utes and set aside to crystallize. Filter and wash the crystals 
with water containing some hydrochloric acid. 

Crystallize the rest of the aminoazobenzene as follows: Dis- 
solve the substance in alcohol in the proportion of 1 gram of 
aminoazobenzene to 10 cc. of alcohol. Heat to boiling and add 
water until the solution begins to cloud; set aside to crystallize. 
Filter off the crystals and wash them with a mixture of equal 
volumes of alcohol and water. 

Aminoazobenzene crystallizes in yellow prisms, melts at 127°, 
and distils undecomposed above 360°. It crystallizes well from 
hot water in which it is difficultly soluble. 


192. Preparation and Properties of Phenylhydrazine (SrcTion 
433).—(a) In a beaker pour slowly, with stirring, 20 grams of 
aniline into 170 cc. of concentrated hydrochloric acid. Cool the 
beaker to 0° in a freezing mixture of ice and salt, and add, drop 
by drop, from a separatory funnel, a mixture of 20 grams of 
sodium nitrite dissolved in 100 cc. of water, until a drop of the 
solution when diluted with a few drops of water produces a blue 
color with iodo-starch paper. (See experiment 187, page 153.) 
The mixture should be stirred during the addition of the sodium 
nitrite. Dissolve 120 grams of hydrated stannous chloride in 
100 cc. of water, cool the solution with ice-water, and pour it 
slowly into the solution of the diazo compound. After an hour 
filter off by suction the precipitate of phenylhydrazine hydro- 
chloride, using a porcelain funnel or a filter-plate and hardened 
filter-paper. Remove as much of the mother-liquor as possible 
by pressing the crystals, and then transfer them to a flask and 
add an excess of a solution of sodium hydroxide. Extract with 


158 EXPERIMENTAL ORGANIC CHEMISTRY 


ether, dry over anhydrous potassium carbonate, and distil off 
the ether. The resulting oil can be used for the following ex- 
periments. If it is desired to keep the phenylhydrazine, it 
should be distilled; as it decomposes slightly on distillation it 
is better to distil it under diminished pressure (§24, page 14). 
The compound can also be purified by freezing it and pouring 
off the liquid which does not solidify. 

Phenylhydrazine is nearly colorless when pure; it melts at 
17.5°, boils at 242°, and has the specific gravity 1.097 at 23°. 
The yield in this preparation should be about 10 grams. 

(b) Conversion of phenylhydrazine into benzene.—Dissolve 35 
grams of copper sulphate in 100 cc. of water in a 500 cc. flask 
connected with a reflux condenser. Heat the solution to boiling, 
remove the flame, and drop into the solution from a separatory 
funnel suspended in the condenser 10 grams of phenylhydrazine 
dissolved in 10 cc. of acetic acid and 50 cc. of water. As soon as 
the phenylhydrazine has been added, arrange the condenser 
for distillation, and distil as long as an oil comes over. Separate 
the oil and shake it with anhydrous calcium chloride until no 
drop of water can be seen, and the benzene is clear. Distil the 
oil and note its boiling-point. 

‘ Benzene, the product of the reaction, boils at 80.4°. The 
yield should be about 6 grams. 

Add 2 drops of phenylhydrazine to Fehling’s solution. 

(c) Formation of a urea derivative from phenylhydrazine: phenyl- 
semicarbazide.—Dissolve 1 cc. of phenylhydrazine in 1 ce. of 
glacial acetic acid and 5 cc. of water, and add a solution of 0.5 
gram of potassium cyanate dissolved in 2 ce. of water. Heat to 
boiling, cool, and shake. Filter off the precipitate, wash with 
cold water, and crystallize it from boiling water. Phenylsemi- 
carbazide melts at 172°. 

(d) Formation of a phenylhydrazone-—Dissolve 2 drops of 
phenylhydrazine in 12 cc. of alcohol, and add 12 cc. of water. 
Add to the solution 2 drops of benzaldehyde and boil for half a 
minute. Cool, shake thoroughly, and filter by suction (§43, 
page 29). Wash with 10 cc. of 50 per cent alcohol, and recrys- 
tallize the precipitate from 25 cc. of boiling 50 per cent alcohol. 
Cool, filter off the crystals, and wash them with 10 cc. of 50 per 


DIAZO COMPOUNDS 159 


cent alcohol. Dry the crystals, and determine their melting- 
point. 

Benzalphenhydrazone is a white crystalline compound which 
melts at 156°. 


Norres.—(b) The reaction between phenylhydrazine and copper sul- 
phate takes place according to the following equation: 


C.H;NH.NH, + CuSO, = C.He -b N, +- Cu + H.S8O, 


(c) Phenylhydrazine is a derivative of ammonia, and its salts, therefore, 
react in many cases like ammonium salts and the salts of amines. The 
preparation of phenylsemicarbazide from phenylhydrazine salts is analagous 
to the preparation of urea from ammonium salts; the equations for the two 
reactions are similar. (See Section 180.) 


NH,Cl + KCNO = NH,.CNO + KCl 
NH,CNO = NH2.CO.NH; 
CeH;NH.NH:2.HCl + KCNO = Co.5H;NH.NH3.CNO + KCl 
CsH;sNH.NH;CNO = C.H;NH.NH.CO.NH, 


(d) Phenylhydrazine is a valuable reagent for identifying aldehydes. 
The method of preparing the phenylhydrazones is illustrated by this experi- 
ment. 


CHAPTER XX 
AROMATIC ALCOHOLS, PHENOLS, AND ETHERS 


193. Preparation of Benzyl Alcohol from Benzaldehyde (Sxc- 
TION 439).—Place in a 250 ce. bottle 20 grams of benzaldehyde 
and a cold solution of 18 grams of potassium hydroxide in 12 cc. 
of water. Close the bottle with a cork or a rubber stopper, 
shake it vigorously until an emulsion is formed, and set aside 
over night or longer. (Hgq.) Add enough water to dissolve the 
crystals of potassium benzoate formed, and extract the solution 
three times with ether, using about 50 cc. each time. Save. the 
aqueous solution. Dry the ethereal solution with anhydrous 
copper sulphate, distil off the ether (§34, page 22), and distil 
the benzyl alcohol. Weigh the alcohol and calculate the per- 
centage yield. 

Benzyl alcohol boils at 206°. The yield in the preparation 
should be about 7 grams. 

Add an excess of hydrochloric acid to the filtered aqueous 
solution of potassium benzoate, filter off the precipitate of benzoic 
acid, and wash it with cold water. Crystallize the acid from 
boiling water. Weigh the acid and calculate the percentage 
yield. 

Benzoic acid melts at 121.4°; it is soluble in 345 parts of water 
at 20°, and in 17 parts at 100°. 


194. Properties of Benzyl Alcohol (Section 439).—(a) Benzyl 
alcohol and hydrochloric acid.—Mix 2 cc. of benzyl alcohol and 
4 ec. of concentrated hydrochloric acid. Heat the mixture slowly 
and note any change produced. (Hq.) Observe the odor of the 
substance formed. : 

(b) Oxrdation of benzyl alcohol—Mix together 1 cc. of concen- 
trated nitric acid, 4 ec. of water, and 3 drops of benzyl alcohol. 
Boil the mixture for about 2 minutes and note the odor from time 
to time. The characteristic odor of benzaldehyde is first ob- 
served, and then disappears as the aldehyde is oxidized further 

160 


AROMATIC ALCOHOLS, PHENOLS, AND ETHERS 161 


to benzoic acid. Cool the solution in running water; if the oxi- 
dation has progressed far enough benzoic acid will crystallize 
out. (Eq@.) 

(c) Benzyl alcohol and acetyl chloride—Add acetyl chloride 
drop by drop, to about 2 cc. of benzyl alcohol as long as evident 
reaction takes place. Pour the product into cold water and 
shake. (Kq.) 


195. Preparation of Diphenylcarbinol from Benzophenone 
(Suction 440).—In a 500 ce. flask dissolve 15 grams of benzo- 
phenone and 15 grams of potassium hydroxide in 150 cc. of 
alcohol. Add 15 grams of zinc dust, connect the flask with a 
reflux condenser and boil for 114 hours. (q.) Filter hot, add 
water until the solution clouds, and set aside to crystallize. 
Filter off the crystals by suction, and wash with dilute alcohol. 
A second crop of crystals may be obtained from the filtrate. 

Diphenylearbinol melts at 67.5°-68°. The yield is nearly 
theoretical. 

Warm a few of the crystals with concentrated hydrochloric 
acid. (q.) 


196. Preparation of Diphenylethylcarbinol by the Grignard 
Reaction (Srctron 349).—In a 200 cc. flask surrounded by cold 
water and provided with a return condenser, place 5 grams of 
magnesium powder, and add slowly through the condenser from 
a separatory funnel a solution of 38 grams of ethyl iodide dis- 
solved in 50 ce. of ether which has been dried over sodium. If 
a reaction does not take place promptly, add a small crystal of 
iodine. ‘Toward the end of the reaction it may be necessary to 
heat the flask by surrounding it with warm water. When the 
magnesium has passed into solution add, drop by drop, through 
the condenser, a solution of 10 grams of benzophenone in 10 
grams of dry benzene. If the reaction ceases, place warm water 
around the flask for afew minutes. Cool the reaction-mixture, 
and pour it slowly into about 200 cc. of ice-water which contains 
about 10 cc. of dilute sulphuric acid. Extract twice with ether, 
using about 100 cc. each time. Shake the ether with a little 
sodium hydroxide solution if it is colored by iodine. Filter the 
ether solution, and distil off the ether; dissolve the residue in 50 


ec. of hot petroleum ether and set the solution aside to crystal- 
11 


162 EXPERIMENTAL ORGANIC CHEMISTRY 


lize. Weigh the product and calculate the yield from the ben- 
zophenone used. 

Diphenylethylearbinol melts at 95°. The yield should be from 
10 to 12 grams. 


PHENOLS 


197. Properties of Phenol (Sections 444, 445).—(a) Solu- 
bility of phenol.—Caution.—Do not touch phenol; it causes pain- 
ful blisters when brought into contact with the skin. Deter- 
mine the solubility of phenol in the following: Water, a solution 
of sodium hydroxide, and a solution of sodium carbonate. Use 
about 1 gram of phenol in each case, and add the liquids in por- 
tions of about 2 cc. until solution is complete; shake thoroughly 
after each addition of the solvent. 

(b) Acidity of phenol.—Test an aqueous solution of phenol 
with litmus paper and with Congo paper. Test a dilute solution 
of hydrochloric acid with the two indicators. Do you observe 
a difference? A much higher concentration of hydrogen ions 
is required to affect the coloring matter on the Congo paper than 
to affect litmus. From the results obtained in experiment 
(a) above what conclusion can be drawn in regard to the relative 
acidity of phenol and carbonic acid? ‘Test a solution of picric 
acid (trinitrophenol), acetic acid, benzoic acid, and salicylic acid, 
with the two indicators. | 

(c) Phenol and acetyl chloride-——Add acetyl chloride, drop by 
drop, as long as an evident reaction takes place, to about 0.5 
gram of phenol. (Hgq.) Pour the product into water and note 
the odor. 

(d) Phenol and ferric chloride—Add a few drops of a dilute 
aqueous solution of ferric chloride (1 part of the 10 per cent 
reagent with 3 parts of water) to an aqueous solution of 
phenol. 

(e) Identification of phenol by converting it into s-tribromphenol. 
—Dissolve about 0.1 gram of phenol in 5 ec. of water and add 
an aqueous solution of bromine until a permanent yellow color 
isformed. Filter off the precipitate and wash it with a solution of 
sulphur dioxide or of acid sodium sulphite until there is a strong 
odor of sulphur dioxide. Wash with water. Dissolve the com- 
pound in 10 cc. of hot alcohol, filter, add 20 cc. of hot water, and 


' AROMATIC ALCOHOLS, PHENOLS, AND ETHERS 163 


set aside to crystallize. Filter off the crystals and dry them on 
a porous plate. Determine the melting-point of the crystals; 
the 2,4,6-tribromphenol which is formed melts at 93°. 


Norrs.—(d) If the ferric chloride solution contains much free acid it will 
not give the usual test—the production of a marked color. If this occurs 
make up a reagent for this and the following experiments as follows: Add to 
a 10 per cent solution of ferric chloride a solution of sodium hydroxide, drop 
by drop, until a permanent precipitate is just formed on shaking. If too 
much alkali is added, a little of the solution of ferric chloride can be used to 
almost dissolve it. Filter the solution, which should have a deep yellow 
color and mix with three volumes of water. 

(e) When bromine is added in excess to an aqueous solution of phenol, a 
compound of the formula Br;CsH2.OBr, is formed, which is converted by 
sulphur dioxide into tribromphenol, Br;CsH2:OH. On account of the great 
insolubility of this compound in cold water, it is of value in detecting the 
presence of phenol in dilute aqueous solutions. Salicylic acid, sulphanilic 
acid, and a few other compounds are converted into tribromphenol by bro- 
mine water. 


198. General Reactions of Phenols (Smctrion 456).—(a) Wirth 
ferric chloride.—Add a dilute aqueous solution of ferric chloride 
(see note to experiment 197d, above) to dilute aqueous solu- 
tions of pyrocatechol quinol, resorcinol, cresol, a-naphthol, 
G-naphthol, and pyrogallol. If no color appears, dissolve a 
little of the substance in alcohol and add a drop of ferric chloride 
solution. 

(b) With bromine water—Add bromine water to the solutions 
of the phenols listed above. 

(c) Preparation of phthaleins from phenols (Srction 473).— 
Put in a dry test-tube about 0.1 gram of phenol, in a second tube 
0.1 gram of resorcin, and in a third 0.1 gram of thymol. To 
each tube add about 0.1 gram phthalic anhydride and 2 drops of 
concentrated sulphuric acid. Place the tube for 3 minutes in an 
oil-bath heated to 160°. Cool, add 5 ce. of a solution of sodium 
hydroxide, and observe the color by transmitted and reflected 
light. If the solution appears to be too concentrated, pour off a 
little and dilute with water. (Kgqs.) 

Notrrs.—(a) Most phenols give a color when treated with a solution of 
ferric chloride. The reaction is valuable in testing for compounds of this 
class. 


(b) Most monatomic phenols which dissolve in water give a precipitate 
when treated with bromine water. 


164: EXPERIMENTAL ORGANIC CHEMISTRY 


199. Preparation and Properties of Anisol (Suction 457).— 
(a) Add to 50 cc. of methyl alcohol, contained in a 250 cc. flask, 
2.5 grams of sodium; the metal should be cut into about half a 
dozen pieces and added slowly, and the flask should be kept cold 
by immersion in water. When the sodium has reacted, add to 
the solution 10 grams of phenol and 20 grams of methyl iodide. 
Attach a reflux condenser to the flask, and heat on a water-bath 
until a drop of the solution, when diluted with water, no longer 
shows an alkaline reaction. The reaction is complete in about an 
hour. Distil off the excess of methyl alcohol on a water-bath, 
and add about 25 cc. of water to the residue. Extract with a 
small amount of ether, dry the ethereal solution with calcium 
chloride, and distil off the ether on a water-bath. Distil the 
residue over a free flame. Calculate the percentage yield from 
the phenol used. 

Anisol boils at 155°. The yield is nearly the theoretical. 

(b) Solubility of anisol—Determine if anisol is soluble in the 
following: dilute hydrochloric acid, dilute sodium hydroxide, 
and cold concentrated sulphuric acid. : 


CHAPTER XXI 
AROMATIC ACIDS 


200. Preparation of Benzoic Acid from Benzyl Chloride (Sxc- 
TION 462).—In a 500 ce. flask provided with a return condenser 
like that shown in Fig. 15, page 26, place 20 grams of benzyl 
chloride, 100 cc. of water, 40 cc. of concentrated nitric acid, and 
half a dozen small pieces from a broken porous plate to prevent 
bumping. Place the flask on a wire gauze and boil for about 
4 hours. When the oxidation is complete, the oil, which at first 
floats, becomes heavier than the aqueous solution, and when the 
flame is removed for an instant sinks to the bottom of the flask. 
Cool under running water, shaking vigorously to avoid the for- 
mation of large lumps. Filter by suction and wash with cold 
water. Dissolve the crystals in the smallest amount of boiling 
water, about 900 cc., add 2 grams of bone-black, boil for 3 min- 
utes, and filter hot; set aside over night to crystallize. Filter 
off the crystals by suction, and wash with cold water. Let the 
acid stand in the air until dry. Weigh and determine the 
melting-point. If the acid does not melt sharply, sublime a 
little of it (§35, page 23),and determine the melting-point again. 
Calculate the percentage yield. How could you readily distin- 
guish a solution of phenol from one of benzoic acid? How could 
you distinguish a solid acid from a solid phenol? How could 
you obtain pure benzoic acid from sodium benzoate? 

Benzoic acid melts at 121.4° and boils at 249°. One hundred 
parts of water at 17.5° dissolve 0.268 parts, and at 75° dissolve 
2.19 parts of the acid. It is readily soluble in alcohol and in 
ether. The yield should be about 14 grams. 


Notr.—In oxidizing aromatic compounds with nitric acid, the latter is 
usually diluted with water in order to prevent nitration. An acid of the 
specific gravity 1.15 is ordinarily used. 


201. Identification of Benzoic Acid: Conversion into Benz- 
anilide.—To definitely identify as benzoic acid an unknown sub- 
165 


166 EXPERIMENTAL ORGANIC CHEMISTRY 


stance which has the melting-point and physical properties of 
this acid, it should be converted into a solid derivative, and 
the properties of this compound determined. Benzanilide, 
CsH;sCO.NHC,.Hs, is conveniently prepared and melts sharply. 
Proceed as follows: To about 0.2 gram of the acid in a dry test- 
tube add about 0.4 gram of phosphorus pentachloride; warm and 
stir the mixture until a homogeneous liquid is obtained. Cool, 
shake with about 5 cc. of water, decant off the latter, and add 
slowly about 1 cc. of aniline. Dissolve the product in a boiling 
mixture of 25 cc. of alcohol and 25 ec. of water. (Filter the 
solution if necessary, cool, and filter off the crystals; wash with a 
little dilute alcohol, and dry the compound at 100°. Determine 
the melting-point. Benzanilide crystallizes in pearly, white 
scales which melt at 160°. 


202. Preparation of Benzamide (Smctrion 465).—Hoop.— 
Place in a small flask 5 grams of benzoic acid and 9 grams of 
phosphorus pentachloride (weighed under the hood), and shake 
and warm on the steam-bath until a clear liquid is formed. Cool, 
and add the liquid to 150 grams of ice and 50 cc. of concentrated 
ammonia in a beaker. Stir occasionally until the liquid has 
changed to a solid. If the substance when pressed with a glass 
rod appears to be plastic, the reaction is not complete; it must 
be more or less granular. Filter by suction, wash with dilute 
ammonia, and crystallize from the smallest possible amount of 
boiling water (about 50 cc.). Weigh the product and determine 
its melting-point. A small amount of amide can be recovered 
from the mother-liquor. 

Benzamide melts at 128°-130°. The yield is about 4 grams. 

Determine whether benzamide shows the properties of an acid 
amide, and describe in your notes the test applied and the result 
obtained. is 


203. Preparation of p-Toluic Acid from the Nitrile (Smcrion 
467).—Hydrolyze the tolunitrile obtained in experiment 189, 
page 154, by heating it with sulphuric acid as follows: For each 
gram of nitrile use 6 grams of concentrated sulphuric acid and 
2 cc. of water. Heat on a sand-bath the mixture contained in a 
flask provided with a wide-bore reflux condenser, until the acid 
sublimes freely into the condenser. Cool, dilute with about 3 


AROMATIC ACIDS 167 


volumes of water, filter off the crystals, and wash them several 
times with cold water. Dissolve the toluic acid in hot alcohol, 
add about 1 gram of bone-black, and boil for 5 minutes. Filter 
hot, and add boiling water until the solution clouds. Set aside 
the solution to crystallize. Filter off the crystals, wash with cold 
water, and dry on a porous plate. Determine the percentage 
yield. A further amount of acid can be obtained from the 
mother-liquor. Save the acid for a later experiment. 

p-Toluic acid melts at 180° and boils at 275°. The yield 
of acid is the theoretical, although some of it is lost in the 
purification. 


204. Preparation of Cinnamic Acid by Perkin’s Synthesis 
(Suction 469).—Place in a small round-bottomed flask provided ~ 
with a reflux air-condenser, in the end of which is a drying tube 
containing calcium chloride, 20 grams of freshly distilled benzal- 
dehyde, 30 grams of acetic anhydride, and 10 grams of freshly 
fused and pulverized anhydrous sodium acetate. (See experiment 
66, page 43.) Heat the mixture in an oil-bath at 170°-180° 
for 8 hours. Pour the mixture into 500 cc. of water, place about 
100 ce. of a 10 per cent solution of sodium carbonate in the flask, 
and shake to dissolve most of the residue. Add this solution to 
the mixture of water and cinnamic acid, heat to boiling, and add 
solid sodium carbonate as long as anything dissolves and the 
solution has a strong alkaline reaction. Stir vigorously during 
the addition in order to bring the oil in contact with the sodium 
carbonate. A small insoluble residue is left. Filter the solution 
hot and add an excess of hydrochloric acid. Filter off the acid 
when the solution has cooled, and wash it with cold water. 
Dissolve the acid in boiling water, add about 2 grams of bone- 
black, boil for 5 minutes, filter hot, and set aside to crystallize. 
Weigh the acid, after drying on a porous plate, determine its 
melting-point, and calculate the percentage yield from the sodium 
acetate used. 

Cinnamic acid melts at 134°; it is soluble in 3500 parts of water 
at 17° and in 100 parts at 100°. The yieldis from 12 to 14 grams. 


205. Properties of Cinnamic Acid (Section 469).—(a) Test 
for the double bond in cinnamic acid.—Dissolve about 0.5 gram 
of the acid in carbon tetrachloride and add, drop by drop, a 


168 EXPERIMENTAL ORGANIC CHEMISTRY 


solution of bromine in the same solvent. If no reaction takes 
place in 1 minute, warm the solution gently. (Hq.) How 
does the rate at which this reaction proceeds compare with the 
rate with which ethylene and bromine react? 

(b) Oxidation of cinnamic acid.—Stir about 0.1 gram of the 
acid with about 5 ec. of a cold 10 per cent solution of potassium 
permanganate and note the odor. (Hq.) What acid would be 
obtained by the further oxidation of cinnamic acid? 


Notr.—(a) The rate at which bromine is added to a double bond is 
determined by the nature of the radicals linked to the carbon atoms joined 
by the double bond; negative atoms or groups markedly retard the reaction. 
In the case of certain compounds which contain four negative groups, for 
example tetraphenylethylene, (Cs6H;)2C =C(CeHs)2, addition does not take 
place at all. 


206. Preparation of Terephthalic Acid from p-Toluic Acid 
(Section 476).—Dissolve 5 grams of the toluic acid prepared in 
experiment 203 in a solution of 3 grams of sodium hydroxide 
in 250 ce. of water. Heat the solution on a water-bath and add 
a solution of 12 grams of potassium permanganate in 250 ce. of 
water until the color of the permanganate persists after heating 
for 5 minutes. Add to the hot solution enough alcohol to react 
with the excess of permanganate, and filter hot. Wash the pre- 
cipitate of manganese dioxide with a little hot water, and add 
an excess of concentrated hydrochloric acid to the filtrate. 
Filter off the terephthalic acid when the solution has cooled. 
Weigh the acid and calculate the yield. Sublime a little of the 
acid. 

Terephthalic acid is almost insoluble in hot and cold water. 
It sublimes without melting. It can be identified most readily 
by converting it into its dimethyl ester as described below. 


207. Preparation of Dimethyl Terephthalate.—In a dry test- 
tube warm together on the steam-bath or in hot water about 
0.2 gram of terephthalic acid and 0.6 gram of phosphorus penta- 
chloride. (Hq.) Cool the mixture and add in small portions, 
keeping the mixture cold in running water, 4 cc. of methyl 
alcohol. (Hq.) Warm the mixture cautiously for a short time 
until reaction is complete. Cool again, add 20 ce. of water, filter 
by suction, and wash the precipitate with 10 ce. of water. Dis- 


AROMATIC ACIDS 169 


solve the dimethyl terephthalate in a boiling mixture of 8 ce. 

of methyl alcohol and 2 cc. of water! Filter hot, using a small 

funnel. Cool, filter off the crystals by suction, and wash them 

with a mixture of 3 cc. of methyl alcohol and 3 cc. of water. Dry 

the crystals on a porous plate and determine their melting-point. 
Dimethyl terephthalate melts at 140°. 


CHAPTER XXII 
AROMATIC ALDEHYDES, KETONES, AND QUINONES 


208. Properties of Benzaldehyde (Srctions 479-482).—(a) 
Oxidation of benzaldehyde.—Leave a few drops of benzaldehyde 
on a watch-glass exposed to the air for a few days. (Hq.) 

Grind a pinch of starch with a few cubic centimeters of cold 
water and pour the mixture into about 50 cc. of boiling water. 
Cool, and dissolve in the solution a crystal of potassium iodide. 
Divide the solution into two portions. Shake one of these with 
2 drops of benzaldehyde and expose both to sunlight for some 
time. Explain. (See Section 480.) 

(b) Test for the aldehyde group in benzaldehyde.—Shake up 
a few drops of benzaldehyde with about 15 cc. of water, and test 
parts of the solution with Fehling’s solution, Tollen’s reagent, 
and Schiff’s reagent. Compare the results with those obtained 
with acetaldehyde. For the test with phenylhydrazine see 
experiment 192d, page 158. If this experiment has not been 
performed, do it now. 

(c) Benzaldehyde and sodium hydrogen sulphite—Shake about 
1 cc. of benzaldehyde with 5 cc. of a saturated solution of sodium 
hydrogen sulphite. Filter off the crystals by suction and wash 
them with a little alcohol until odorless. Dissolve the crystals 
in warm water; to one-half of the solution add a solution of sodium 
carbonate, and to the other dilute sulphuric acid. Explain the 
cause of the appearance and odor produced. 

(d) Benzaldehyde and sodium hydroxide.—Shake up a few drops 
of benzaldehyde with a solution of sodium hydroxide, and then 
warm the mixture. Is a resin formed? Compare the results 
with those obtained in the case of acetaldehyde (experiment 
108d, page 83). For the behavior of benzaldehyde with alkalies 
see experiment 193, page 160. 

(e) Benzaldehyde and ammonia: hydrobenzamide-——Mix to- 
gether 3 cc. of benzaldehyde, 20 cc. of alcohol, and 10 cc. of a 

170 


AROMATIC ALDEHYDES, KETONES, AND QUINONES 171 


concentrated solution of ammonia. Set aside the mixture until 
the product which separates becomes solid. Heat on the steam- 
bath, and add alcohol until the solid dissolves. Set aside to 
crystallize. Determine the melting-point of the crystals. Com- 
pare the behavior of formaldehyde, acetaldehyde, and benzalde- 
hyde with ammonia. 

Hydrobenzamide, (CsH;CH)3Nse, crystallizes from alcohol in 
octahedra which melt at 110°. 


209. Preparation of Benzophenone (Srctions 487 and 348).— 
In a dry 500 cc. flask put 25 grams of benzene, 25 grams of 
benzoyl chloride, 50 cc. of carbon bisulphide, and 30 grams of 
anhydrous aluminium chloride. The aluminium chloride should 
not be exposed to the air any longer than necessary, as it rapidly 
absorbs moisture. Connect the flask with a reflux condenser 
and heat it on a water-bath. The reaction is complete when a 
few drops of the solution in the flask, when treated with a little 
water, give an oil which does not have the disagreeable odor of 
benzoyl chloride. The time required is from 3 to 4 hours. Cool 
the flask in water, and pour the contents into about 300 cc. of 
water to which has been added 20 cc. of concentrated hydrochloric 
acid. Separate the layer of carbon bisulphide in which the ben- 
zophenone is dissolved, and evaporate off the solvent on the 
steam-bath in the hood, away from any flames. If no steam- 
bath is available, place the solution in a flask and distil off the 
solvent on a water-bath through a long condenser. Add 50 
ee. of alcohol and 2 grams of bone-black, boil for about 5 minutes, 
and filter hot. Wash the bone-black with a few cubic centimeters 
of hot alcohol. When the filtrate is cold, add cold water until a 
slight permanent cloud is produced, and set aside to crystallize. 
If an oil separates, scratch the inside of the beaker just below the 
surface of the solution with a glass rod. At the end of'some hours 
or at the next exercise, filter off the crystals by suction and wash 
them twice (§12, page 7) with a mixture of 2 volumes of 
alcohol and 1 of water. A further amount of benzophenone can 
be obtained by adding to the filtrate from the crystals cold 
water until the solution clouds, and proceeding as above. 

Weigh the product and calculate the percentage yield from the 
benzoyl chloride used. Write equations for all the reactions in- 
volved, including those into which the aluminium chloride enters. 


172 EXPERIMENTAL ORGANIC CHEMISTRY 


Benzophenone melts at 48°, and boils at 306.1°. The yield in 
the preparation is about 20 grams. 


210. Preparation of Benzophenoneoxime (SEcTIon 488).—In 
a flask provided with a reflux condenser dissolve 5 grams of 
benzophenone in 50 cc. of alcohol, and add a solution of 5 grams 
of hydroxylamine hydrochloride in 15 ce. of water; to this add a 
solution of 10 grams of sodium hydroxide in 15 ce. of water, and 
heat the mixture on a water-bath for an hour. Pour the product 
into about 200 cc. of water, filter if necessary, and add to the fil- 
trate dilute sulphuric acid until the solution is just acidic to lit- 
mus paper. After an hour filter off the benzophenoneoxime. 
Weigh the product when dry and calculate the percentage yield, 
which should be nearly theoretical. Recrystallize the oxime 
from about 25 ec. of hot alcohol. 

Benzophenoneoxime melts at 141°. 


211. Beckmann’s Rearrangement of an Oxime (SECTION 
488).—In a small flask dissolve 2 grams of benzophenoneoxime 
in 30 cc. of ether dried over sodium, and add slowly in small 
portions 3 grams of finely divided phosphorus pentachloride. 
At first it may be necessary to cool the solution; toward the end 
of the reaction the mixture should be heated on the steam-bath 
until the phosphorus pentachloride has dissolved. When this 
has taken place, pour the ethereal solution with vigorous stirring 
into 400 ce. of cold water. Stir until a solid has formed, and then 
filter it off by suction and wash with cold water. Crystallize 
the benzanilide from the smallest amount of boiling alcohol, and 
determine the melting-point of the dried crystals. Write equa- 
tions for the reactions involved in the rearrangement. 

Benzanilide melts at 163°. 


212. Preparation of Quinone (Srcrion 492).—Mix in a large 
beaker 250 cc. of water, 50 cc. of pure concentrated sulphuric 
acid, and 50 grams of sodium bichromate or the equivalent weight 
of potassium bichromate. When the salt has dissolved, set the 
beaker in cold water and cool the solution to 20°. Mix in a 
beaker 150 ce. of water and 10 grams of aniline; pour into the 
mixture, with stirring, 10 cc. of pure concentrated sulphuric 
acid. Cool the solution to 20° and add it, stirring vigorously, 


AROMATIC ALDEHYDES, KETONES, AND QUINONES 173 


in four portions to the solution of sodium bichromate. The 
beaker in which the reaction takes place should be surrounded by 
cold water and the temperature should be kept between 35° and 
40°. About 6 to 8 minutes are required for the addition of the 
solution of aniline sulphate. When this has been accomplished, 
remove the beaker from the water and let it stand for about 
15 minutes. Transfer the product to a large flask, and cool it in 
running water to about 15°. Add to the flask 300 cc. of ether 
and shake. Let the flask stand for a few minutes. In order to 
facilitate the separation of the ether into a distinct layer, add to 
it 25 cc. of acetone, and give to the flask a gentle rotary motion. 
In a few minutes decant off carefully as much of the ether as 
possible into a separatory funnel; if some of the aqueous layer 
flows into the funnel it can be separated. Draw off the ethereal 
solution, place it in a flask, and distil the ether off from a water- 
bath through a long water-jacketed condenser (see $34, page 
22). Extract the solution of quinone once more with this re- 
covered ether, and evaporate it off as before. Crystallize the 
residue of quinone from the smallest possible amount of boiling 
ligroin, or distil it with steam in the ordinary way except that 
no water is put into the flask containing the quinone. Dry 
the crystals of quinone in a desiccator; the compound is volatile 
at room temperature, and if left exposed to the air for a number 
of hours an appreciable quantity is lost. 

Quinone melts at 116°. The yield in this preparation is 5 
to 6 grams. 


213. Properties of Quinone (Suction 492).—(a) Reduction of 
quinone.—Shake up a crystal of quinone with 10 cc. of water. 
Note the odor and color of the solution; add to one-half of it a 
solution of sodium hydrogen sulphite. (Hq.) To the other half 
add a dilute solution of potassium iodide and a few drops of 
dilute hydrochloric acid. (Kq.) 

(b) Unsaturation of quinone.—Dissolve a few crystals of quin- 
one in 5 cc. of carbon tetrachloride and add, drop by drop, a 
solution of bromine in carbon tetrachloride. (Hq.) 

(c) Formation of quinhydrone—Make a saturated solution of 
quinone in water and add to the solution, drop by drop, a strong 
aqueous solution of hydroquinone. Examine the tube after about 


174 EXPERIMENTAL ORGANIC CHEMISTRY 


1 minute. If crystals have not formed, repeat, using a more con- 
centrated solution of hydroquinone. (Hq.) Add a solution of 
ferric chloride to a strong solution of hydroquinone. (£q.) 
Add an ammoniacal solution of silver nitrate to an aqueous solu- 
tion of hydroquinone. 


214. Preparation of Anthraquinone (Section 494).—In a 
250 ce. round-bottomed flask provided with a reflux condenser 
place 5 grams of anthracene and 50 cc. of glacial acetic acid. 
Heat the liquid to boiling over a wire gauze and add, drop by 
drop, from a separatory funnel placed in the upper end of the 
condenser, a solution made by dissolving 10 grams of chromic 
acid anhydride in 10 ce. of water and then adding 25 ce. of glacial 
acetic acid. Boil the solution for 10 minutes after the oxidizing 
agent has been added, and then allow the mixture to cool spon- 
taneously to the temperature of the room. Finally cool under 
running water. Filter by suction, and wash the crystals twice 
with a mixture of 2 volumes of water and 1 volume of glacial 
acetic acid, using 20 cc. of the mixture each time. Finally wash 
twice with water and allow the crystals to dry in the air. 

Sublime a small amount of the dried anthraquinone (§35, 
page 23), and crystallize a little from boiling alcohol. 

Anthraquinone sublimes at about 250° in yellow needles 
which melt at 273°. The yield in this preparation is 5 grams. 

Boil together for about halfaminutea trace of powdered anthra- 
quinone with a little zinc dust and 10 ce. of a solution of sodium 
hydroxide. Filter the solution and shake it with air. Anthra- 
quinone is partly reduced by zine and sodium hydroxide to a 
red salt of the composition: 


CO aN 
C.H ie CeH 
ON CHIONA) 7 am 
This salt is oxidized by air to anthraquinone. The reaction is 
a valuable one in the identification of this substance. 

Compare the properties of anthraquinone with those of benzo- 
quinone. Does the former oxidize an acidified solution of potas- 
sium iodide? Is it reduced by sulphurous acid? 

Notre.—After oxidation by chromic acid in acetic acid solution, the prod- 
uct is usually precipitated by pouring the solution into water. In the case 


of anthraquinone it is convenient to allow the mixture to cool as the com- 
pound crystallizes well from glacial acetic acid. 


CHAPTER XXIII 


AROMATIC COMPOUNDS CONTAINING TWO OR MORE UNLIKE 
' GROUPS 


215. Preparation of o-Nitrophenol (Section 498).—In a small 
beaker melt 20 grams of phenol on the steam-bath, and add it 
slowly with stirring to a mixture of 30 cc. of pure concentrated 
nitric acid and 100 grams of ice contained in a beaker. . Stir 
the mixture and then let it stand for at least 3 hours; if more con- 
venient it can be set aside until the next laboratory exercise. . 
Decant off as much of the acid layer as possible through a funnel 
containing a filter-paper, which serves to collect the part of the oil 
that is suspended in water. Add about 200 ce. of water to the 
oil, stir, and decant off the liquid as before. Repeat the washing 
with 200 cc. of water. Place the filter-paper with the adhering 
oil in a liter flask, arranged for steam distillation (see Fig. 12, 
page 19). Wash the oil in the beaker into the flask using for 
the purpose 200 cc. of water, which should be measured. (This 
is done to facilitate the isolation of the p-nitrophenol which is not 
volatile with steam.) Distil with steam as long as any oil or 
solid condenses (about 30 minutes). If the oil solidifies in the 
condenser, turn off the water from the latter; when the water in 
the condenser becomes heated, the solid melts and runs into the 
receiver. Filter, dry, and weigh the o-nitrophenol. Recrystal- 
lize the product by dissolving it in 40 cc. of hot alcohol and adding 
AO cc. of water; set aside over night to crystallize. Filter by 
suction and wash with a small amount of cold alcohol. Heat the 
filtrate to boiling and add an equal volume of water. Set aside 
and collect as before. 

o-Nitrophenol melts at 45°. The yield is from 7 to 8 grams. 

The p-nitrophenol, which is not volatile with steam, may be 
obtained from the residue in the flask as follows: Cool in running 
water the solution in the flask to 40° and filter it rapidly through 
a large funnel. The volume of the solution should be about 300 
ee. Add 2 grams of bone-black to the filtrate and boil it for about 

175 


176 EXPERIMENTAL ORGANIC CHEMISTRY 


15 minutes. Filter hot, and place in cold water. The solution 
should be cooled to at least 10°, and ice should be used if neces- 
sary. If crystals do not form, scratch the side of the beaker with 
aglass rod. After standing for about half an hour, filter off the 
crystals by suction and wash them with a little cold water. The 
yield is about 3 grams. By evaporating the mother-liquor to 
dryness on the steam-bath and extracting the residue with 
about 50 cc. of boiling benzene, about 2 grams more of the prod- 
uct can be obtained. 

p-Nitrophenol melts at 114°; it crystallizes well from benzene 
in which it is readily soluble hot and difficultly soluble cold. 
When pure it crystallizes readily from hot water. 

Compare the conditions used in the nitration of phenol with 
those used in making nitrobenzene (experiment 170, page 135), 
dinitrobenzene (experiment 172, page 137), and nitroacetanilide 
(experiment 219, page 178). 


Notse:—The yields are small in this preparation on account of the fact 
that compounds other than o- and p-nitrophenol are formed; among these 
are substances of a tarry nature from which it is difficult to separate the para- 
compound. It is on this account that special precautions are necessary in 
order to obtain p-nitrophenol in a crystalline condition. 


216. Isolation of Eugenol from Cloves (Sxctron 505).—Distil 
25 grams of cloves with steam as long as an oil separates in the 
condenser; during this time about 600 cc. of water will distil. 
Give the vessel containing the mixture a rotary motion so that 
the oil settles. Decant off most of the water, and pour the oil 
into a test-tube. By means of a pipette transfer about one-half 
the oil to a small test-tube, cover it with about 2 cc. of water, and 
add a dilute solution of sodium hydroxide (10 per cent) as long as 
it appears to dissolve the oil. (Hq.) Isaclear solution obtained? 
Add to a few cubic centimeters of the alkaline solution, bromine- 
water in excess. What does the reaction indicate? Divide the 
rest of the alkaline solution into two equal portions. To one add 
an excess of dilute hydrochloric acid. (Hgq.) Set the two tubes 
aside and examine them carefully at the next exercise for an oil. 
Explain why sodium hydroxide did not dissolve the oil to a clear 
solution. 

Separate from water, by means of a pipette, the rest of the oil 
obtained in the distillation with steam. Put it in a dry test- 


AROMATIC COMPOUNDS 177 


tube, avoiding getting water into the tube. Add about 2 ce. 
of carbon tetrachloride, and filter into a dry test-tube through a 
small funnel containing a paper moistened with carbon tetra- 
chloride. Add a solution of bromine in carbon tetrachloride, 
drop by drop. What does the behavior indicate? 


217. Preparation of Sulphanilic Acid (Section 510).—In a 
small round-bottomed flask containing 25 grams of aniline, pour 
cautiously 80 grams of pure concentrated sulphuric acid. Heat 
the mixture for from 4 to 5 hours in an oil-bath at 180°-190°. 
In order to determine whether the reaction is complete, remove a 
drop of the mixture on a glass rod, and mix it on a watch-glass 
_ with a few drops of a solution of sodium hydroxide. If any 
aniline sulphate is present in the mixture, the aniline will separate 
as an oil; if sulphonation is complete, the sodium salt of sulph- 
anilic acid, which is soluble in water, is formed. When the 
reaction is complete, pour the product into about 300 cc. of cold 
water. Filter, wash the precipitated sulphanilic acid with cold 
water, dissolve it in boiling water, avoiding an excess of the latter, 
add about 2 grams of bone-black, and boil for 5 minutes, stirring 
occasionally. Filter the hot solution and set aside to ecrystal- 
lize. Dry the crystals in the air; weigh them as soon as dry as 
the acid slowly loses its water of crystallization on standing. 
Calculate the percentage yield. 

Sulphanilic acid crystallizes from water in plates, which con- 
tain 2 molecules of water of crystallization; it is converted into 
tribromaniline by an excess of bromine water. The yield in 
this preparation is about 25 grams. 


218. Preparation of m-Nitraniline (Section 511).—In a 100 
ec. flask dissolve 10 grams of m-dinitrobenzene in 50 ce. of hot 
alcohol; cool the solution under running water so that small 
crystals are formed, and add 10 cc. of a concentrated solution of 
ammonia in water. Hoop.—Pass into the solution a rapid 
stream of hydrogen sulphide as long as heat is evolved by the 
reaction (Hq.); this requires about one-half hour. Heat on the 
steam-bath for 10 minutes. Pour the product into 200 cc. of 
water, filter by suction, and wash the precipitate with water. 
Put the mixture of m-nitraniline and sulphur into a beaker, add 


100 ec. of water and 20 ce. of concentrated hydrochloric acid, stir, 
12 


178 EXPERIMENTAL ORGANIC CHEMISTRY 


and filter off the residue of sulphur by suction. Set the filtrate 
aside. Determine whether all the nitraniline has been extraeted 
from the sulphur by treating it on the filter with a little dilute 
hydrochloric acid, and adding ammonia to the filtrate. To the 
original filtrate from the sulphur add an excess of concentrated 
ammonia. Cool in running water, filter off the precipitated m- 
nitraniline by suction, and wash it with a little cold water. Dis- 
solve the nitraniline in the smallest amount of boiling water 
(about 500 cc.), filter the hot solution, and set it aside to crys- 
tallize. Filter off the crystals, wash them with a little cold 
water, and dry on filter-paper. Calculate the percentage yield 
and determine the melting-point of the product. 

m-Nitraniline crystallizes in yellow needles, which melt at. 
114°. The yield in this preparation is from 5 to 6 grams. 


219. Preparation of p-Nitraniline (Section 511).—Add slowly 
in small amounts with stirring, 20 grams of finely powdered 
acetanilide to 60 grams of fuming nitric acid (sp. gr. 1.52) contained 
in a beaker surrounded by ice and concentrated commercial 
hydrochloric acid. The temperature of the nitric acid should 
not be allowed to rise above 10°. The addition of the acetanilide 
requires about 20 minutes. When the substance has dissolved, 
pour the solution into about 300 cc. of cold water, stir vigorously, 
and filter by suction. p-Nitroacetanilide is precipitated, and 
the ortho compound formed remains in solution. Wash the pre- 
cipitate three or four times with hot water. Remove as much 
water as possible by pressing the compound on the funnel, and 
then crystallize it from boiling alcohol. Let the solution cool, 
and filter off the crystals. By evaporating the filtrate to a small 
bulk, a further amount of the anilide can be obtained. Deter- 
mine the melting-point and yield of the p-nitroacetanilide 
obtained. | 

p-Nitroacetanilide melts at 207°. The yield should be about 
14 grams, The ortho compound can be obtained from the origi- 
nal solution in dilute nitric acid by extraction with chloroform. 

To obtain p-nitraniline from the anilide proceed as follows: 
Hoopv.—In a beaker covered with a watch-glass boil the acet- 
p-nitranilide with ten times its. weight of dilute hydrochloric 
acid (sp. gr. 1.12) for about 20 minutes. Cool the solution, add 


t 


AROMATIC COMPOUNDS 179 


about an equal volume of water and an excess of concentrated 
ammonia. When the solution is cold, filter off the p-nitraniline, 
wash it with cold water, recrystallize from boiling water, using 
about 60 cc-of water for each gram of anilide hydrolyzed. Weigh 
the compound, determine its melting-point, and calculate the 
percentage yield from the p-nitranilide used. 

p-Nitraniline melts at 147°. 


220. Hydrolysis of the Salts of the Nitranilines.—Prepare a 
sample of aniline hydrochloride as follows: Mix together 1 ce. 
of aniline and 1 ec. of concentrated hydrochloric acid. Cool 
under running water, and place the solid which separates on a 
porous plate. When the liquid has been absorbed pour a little 
ether on the salt. Repeat the treatment with ether, and let the 
salt dry in the air. Prepare samples of the hydrochlorides of 
meta- and para-nitranilinesasfollows: Mixtogetherabout 1 gram 
of the amine with 5 cc. of concentrated hydrochloric acid and 5 
ec. of water. Heat to boiling, and then cool in running water. 
Filter the salt by suction, and wash the crystals with 10 ce. of 
alcohol and then with 10 cc. of ether. Dry the salts for a few 
minutes on filter-paper. 

Shake up a little of the three salts with about 2 cc. of water 
and test the solutions for acid with litmus paper and with Congo 
paper. Explain the results. 

Nore.—Litmus is much more sensitive to hydrogen ions than the dye on 
Congo paper. 

221. Properties of Salicylic Acid (Secrion 516).—(a) Salicylic 
acid and ferric chloride.—Add a dilute solution of ferric chloride 
(see note to experiment 197d, page 163) to a dilute aqueous 
solution of a salicylic acid. To one-half of the solution add 
dilute hydrochloric acid, drop by drop, and to the other half 
dilute acetic acid. Add a drop of ferric chloride to an alcoholic 
solution of salicylic acid. Repeat these tests with phenol and 
compare the results. | 

(b) Salicylic acid and bromine.—Add bromine water to a solu- 
tion of the acid. (Kq.) 

(c) Formation of methyl salicylate——Warm together on a watch- 
glass about 0.05 gram of salicylic acid, 3 drops of methyl alcohol 
and 3 drops of concentrated sulphuric acid. (Hqg.) Note the 
odor of the compound formed. 


180 EXPERIMENTAL ORGANIC CHEMISTRY 


(d) Decomposition of salicylic acid on heating.—Heat rapidly 
in a dry test-tube a little of the acid (£q.) and note the odor. 

(e) Detection of salicylic acid and benzoic acid in foods.—If the 
sample to be tested is a liquid, acidify 100 cc. of it with 10 drops 
of dilute sulphuric acid, and extract the solution twice with 
ether or petroleum ether, using 50 cc. each time. If the material 
contains a substance insoluble in water, grind 50 grams of it 
with 100 ec. of water, and add enough of a dilute solution of 
-sodium hydroxide to makethemixturealkaline. Muixthoroughly, 
filter through 3 layers of cheese-cloth, acidify with dilute 
sulphuric acid, and extract twice with ether or petroleum ether 
using 50 ec. each time. Separate the ethereal extract and filter 
it through a dry filter-paper. Shake 5 cc. of the extract with 
5 cc. of water and add to the aqueous solution a dilute solution 
of ferric chloride containing no free acid; if salicylic acid is 
present, the characteristic color will develop. Evaporate the 
rest of the ethereal extract to dryness, dissolve the residue in the 
smallest possible amount of hot water., Let the solution cool, 
and remove the crystals by means of a spatula to a porous plate. 
When dry, determine their melting-point. Test a crystal with 
ferric chloride as in (a) above. Dissolve a crystal in a drop of 
ammonia, evaporate on the steam-bath, dissolve in a few drops 
of water, and add a drop of a solution of ferric chloride. If 
benzoic acid is present, a buff-colored precipitate of basic ferric 
benzoate is formed. 


222. Properties of Tannic Acid (Sections 523, 524).—For 
the following experiments make a 1 per cent solution of tannic 
acid, by dissolving 0.5 gram of the acid in 50 ce. of water. 

(a) Tannic acid and ferric chloride—Add a few drops of 
a dilute solution of ferric chloride (see note to experiment 
197d, page 163) to about 5 cc. of a solution of tannic acid. 
Dilute some of the solution of the acid with 50 parts of water 
and add a drop of ferric chloride. 

(b) Tannic acid and the salts of heavy metals —Add to a solu- 
tion of the acid a solution of lead acetate. Repeat using copper 
sulphate. 

(c) Tannic acid and gelatin.—Dissolve about 0.1 gram of 
gelatin in about 10 cc. of warm water, and add to one-half of the 


+ 


AROMATIC COMPOUNDS 181 


cold solution a solution of tannic acid. Reserve the rest of the 
solution for experiment (f) below. 

(d) Reducing action of tannic acid.—Test a solution of the 
acid with Fehling’s solution. Add a solution of tannic acid to 
an ammoniacal solution of silver nitrate. 

(e) Oxidation of tannic acid by air.—Mix a little of the solu- 
tion of the acid with a solution of sodium hydroxide and shake 
the mixture in contact with air. 

(f) Tannic acid in tea (Section 526).—Pour about 50 cc. of 
boiling water onto about 1 gram of tea. After 2 minutes decant 
off the clear solution; to 5 cc. of it add 2 drops of ferric chloride 
solution. If the shade of the color produced can not be clearly 
seen, dilute with water. Compare the color with that produced 
by the gall-nut tannic acid in experiment (a) above. Add 5 ce. 
of the solution to a dilute solution of gelatin. Compare the 
behavior of the tannic acid from tea with that from gall-nuts. 

To the rest of the tea-infusion add a dilute solution of lead 
acetate, drop by drop, from a pipette as long as a precipitate 
is formed. 

Devise and carry out an experiment to determine whether the 
amount of tannic acid present in a tea-infusion is greater when 
the tea is steeped for 2 minutes, or when it is boiled with water 
for 15 minutes. 

(g) Preparation of a tannin ink: removal of ink-stains (Sxc- 
TION 525).—Dissolve 1 gram of tannic acid in 10 ce. of hot water, 
0.5 gram of ferrous sulphate in 5 cc. of hot water, and 0.05 gram 
gum arabic in 5 ce. of hot water. Cool the solutions and mix 
them. Write on a piece of paper with some of the ink, using a 
new pen. Add a few drops of ferric chloride to a little of the 
ink and write with the mixture. Compare result in the two cases. 
Explain. Put the paper away, and examine the writing with the 
two samples of ink at the next exercise. Explain. 

Put on a piece of cotton cloth some of the iron ink and on an- 
other piece some ordinary ink which probably contains a dye. 
When the ink-spots are dry, cut each piece of cloth into three 
parts in such a way that the pieces containing the iron ink can 
be distinguished from those containing the dye. Wash the pieces 
in water. Add a piece of each kind to a dilute solution of oxalic 
acid. Explain the result. Add a piece of each kind to a dilute 


182 EXPERIMENTAL ORGANIC CHEMISTRY 


solution of sodium hypochlorite. Place these pieces alternately 
in the solution of oxalic acid and sodium hypochlorite until the 
color is destroyed in both cases. 

Prepare a 0.5 per cent solution of potassium permanganate by 
dissolving about one-fourth gram of the salt in 50 cc. of water. 
Add to the solution 5 drops of concentrated sulphuric acid. 
Place in the solution pieces of cloth containing the two kinds 
of ink. After about 2 minutes remove them, wash with water, 
and place them in a strong solution of sodium hydrogen sulphite. 
Repeat the treatment with the permanganate and sulphite until 
the ink is destroyed. - If ink is removed in this way the fabric 
should be washed thoroughly in water, and then placed in a 
dilute solution of ammonia. 


Notrs.—(b) The formation of insoluble compounds from tannic acid 
and the salts of metals is used in preparing mordants in dyeing. (See 
experiment 228, page 187.) 

(c) The use of tannin in tanning leather is based on the fact that it forms 
a compound with the proteins in the hide, of which gelatine is an example. 

(g) The removal of ink-spots from fabrics made of silk is best accom- 
plished by means of potassium permanganate. If sodium hypochlorite is 
used,the chlorine present attacks the material, and converts it into a chlorin- 
ated product which has a faint yellow color that can not be readily destroyed. 
A neutral solution of potassium permanganate oxidizes ink; the reaction 
takes place more rapidly in a very faintly acid solution. 


CHAPTER XXIV 
DYES AND DYEING 


223. Preparation of an Azo Dye: Methyl Orange (SrectTion 
534).—Dissolve 10 grams of sulphanilic acid and 3 grams of 
anhydrous sodium carbonate in 150 ce. of water. To the solu- 
tion first add 4 grams of sodium nitrite dissolved in 20 cc. of 
water, and then a mixture of 7 cc. of concentrated hydrochloric 
acid and 10 ce. of water. (Hq.) Dissolve 6 cc. of dimethylani- 
line in a mixture of 20 cc. of water and 10 cc. of concentrated 
hydrochloric acid. Cool the solution under running water, and . 
pour it slowly and with stirring into the diazotized sulphanilic 
acid. (Hq.) Add a dilute solution of sodium hydroxide until 
the solution is just alkaline; this can be seen by the change in 
color. Add to the mixture 50 grams of salt dissolved in 150 
cc. of water. In order to facilitate the separation of the dye, 
heat the mixture to boiling until gas-bubbles disappear. Allow 
the solution to cool to room temperature, and filter it with a large 
funnel, without the use of suction. When the liquid no longer 
passes through the filter-paper, transfer the precipitated dye, 
which is mixed with much water, to a funnel connected with 
a filter-bottle and pump, and remove the last part of the solvent 
by suction. It is well to proceed in the way described, and 
not to attempt to filter by suction at first; in this case the paper 
soon becomes clogged with the dye and filtration proceeds very 
slowly. | 

The salt may be purified by recrystallization from hot water 
(about 150 cc.). Filter the boiling solution in the way described 
in §10, page 6. The yield should be about 12 grams. 

Dissolve a little methyl orange in water and add alternately 
to the solution dilute hydrochloric acid and dilute sodium hy- 
droxide as long as a change in color is observed. (Kqs.) 

Dissolve about 0.2 gram of methyl orange in about 10 ce. of 
dilute hydrochloric acid, add about 1 gram of zine dust and boil 

183 


184 EXPERIMENTAL ORGANIC CHEMISTRY 


the solution as long as any change takes place. Methyl orange, 
like other azo dyes, is reduced to colorless compounds by hydro- 
gen in acid solution at the N: N bond: 


(CH3)e2NCeHiN : NCeH4SO3H =e 4H = (CH3)2NCeH4N He +- 
H.2NC,.H.803H 


224. Preparation of a Triphenylmethane Dye: Malachite 
Green (Section 541).—Melt cautiously over a flame in a 6-inch 
evaporating dish 7 grams of fused zine chloride, as long as bubbles 
are given off. Remove the flame and as the zinc chloride cools 
rotate the dish slowly so that when cold the chloride covers an 
area from 3 to 4 inches in diameter. Put into the dish 13 grams 
of dimethylaniline and 5 grams of freshly distilled benzaldehyde. 
Cover the dish with a watch-glass and heat on the steam-bath 
for 4 hours. Stir the contents frequently with a glass rod, which 
should be left in the mixture. Transfer the reaction-product 
to a flask; the part that can not be poured out of the evaporating 
dish can be treated repeatedly with hot water and thus removed. 
Distil with steam as long as any oil passes over. Discard the 
distillate. Pour the water out of the flask and dissolve the mate- 
rial sticking to the side of the flask in the smallest amount of 
boiling alcohol. Filter the solution and set it aside to crystallize 
over night. The leuco base which separates may form at first 
as an oil, but on standing changes into masses of small crystals, 
Filter off the solid, dry and weigh it. The yield of leuco base, 
CeHsCH[CsHsN(CHs3)e]2, should be from 7 to 10 grams. 

To convert the leuco base into the color base it is oxidized by 
lead dioxide. The dye is finally obtained as the double chloride 
of the color base and zine chloride. Prepare the lead dioxide 
as follows: Dissolve 8 grams of lead acetate in 50 cc. of water. 
Mix thoroughly 20 grams of fresh bleaching powder with 300 cc. 
of water and filter. Heat the solution of lead acetate, and add 
the solution of bleaching powder slowly, keeping the solution 
just below boiling. When all the lead has been precipitated and 
the solid has changed to a deep brown color, stop heating and ~ 
let the precipitate settle. Pour off the liquid and wash the solid 
three times by decantation, using about 500 ce. of water each 
time. 

Dissolve 5 grams of the leuco base in a mixture of 5 ce. of con- 


DYES AND DYEING 185 


centrated hydrochloric acid and 10 cc. of water. Pour this into 
a large beaker containing 400 cc. of water and 100 grams of ice. 
Stir, and add slowly, taking about 5 minutes for the operation, 
the lead dioxide from which as much water as possible has been 
removed by decantation. Next add a solution of 5 grams of 
sodium sulphate in 25 cc. of water; this is to precipitate the lead 
which has gone into solution as chloride. Filter, and to the fil- 
trate add a solution of 5 grams of zine chloride in 10 ec. of water. 
To precipitate the dye add 50 grams of powdered salt, and stir 
until the latter has dissolved. Filter with a large funnel, and 
finally transfer the dye, which is mixed with much water, to a 
funnel connected with a pump, and remove most of the solution 
by suction. Wash once with a solution of salt. Transfer the 
dye to a porous plate. When quite dry, weigh the compound. 
Write equations, using graphic formulas, for all the reactions in- 
volved in the preparation. The yield should be 7 grams. 


' 225. Preparation of a Phthalein: Fluorescein (Srctions 543, 
545).—Melt cautiously over a flame in a 6-inch evaporating dish, 
5 grams of anhydrous zine chloride, as long as bubbles are given 
off. When the zinc chloride solidifies, add 10 grams of resorcin 
and 7 grams of phthalic anhydride. Cover the dish with a watch- 
glass, place it on a wire gauze, and heat very carefully over a 
flame about 2 cm. high, the top of which is 2 or 3 cm. below 
the gauze. (Hq.) The heating should be at such a rate that the 
mixture produces bubbles slowly. In about 15 minutes, when 
the bubbles cease to be formed and the mass becomes stiff, stop 
the heating, and add to the dish, after it has cooled somewhat, 
100 ce. of water and 20 cc. of concentrated hydrochloric acid. 
Heat the mixture to boiling, and break up with a glass rod the 
mass on the bottom of the dish. In a few minutes pour off the 
liquid through a filter and grind the solid with a pestle. Add 100 
ec. of water and 20 cc. of concentrated hydrochloric acid, and boil 
again. Finally filter and wash with water. Let the fluorescein, 
the insoluble residue, dry in the air. Weigh the product. The 
yield should be about 12 grams. 

Fluorescein can be crystallized by dissolving it in hot alcohol 
or in hot glacial acetic acid, and adding water. 

Dissolve a trace of fluorescein in a dilute solution of sodium 


186 EXPERIMENTAL ORGANIC CHEMISTRY 


hydroxide and examine the solution by reflected and by trans- 
mitted light. 

226. Preparation of Eosin (Srcrion 545).—In a small flask 
cover 5 grams of fluorescein with 20 cc. of aleohol. Add slowly 
in small portions, taking 10 minutes for the operation, 4 cc. 
of bromine. Shake the flask frequently. When about one-half 
of the bromine has been added most. of the fluorescein passes 
into solution as the dibrom-substitution-product; as the addi- 
tion continues the tetrabrom-substitution-product crystallizes 
out. (Hq.) Allow the mixture to stand for an hour; filter and 
wash twice with a small amount of cold alcohol. The yield is 
about 7 grams. 

Dissolve a little eosin in sodium hydroxide and examine the 
solution by transmitted and by reflected light. 

Salts of eosin are used for dyeing. Prepare some of the ammo- 
nium salt as follows: Placein a desiccator about 25 cc. of con- 
centrated ammonia. Place about a gram of powdered eosin on 
asmall watch-glass and support it on a triangle in the desiccator. 
Cover the latter. At the next exercise test the solubility of the 
substance on the watch-glass; it if has been completely converted 
into the ammonium salt it will dissolve without a residue in water. 

Dissolve some of the ammonium salt in a little water, and then 
use the solution as ink, with a new pen. 

Dissolve about 0.1 gram of the salt in 200 ce. of water and dye 
a piece of silk by heating it with the solution for about 10 minutes. 


DYEING 


227. Dyeing with a Substantive Dye: Congo (Srcrions 528— 
530, 534).—The cotton to be used in this and the experiments 
which follow should be heated for 10 minutes in a boiling solution 
of 1 gram of sodium carbonate in 500 cc. of water. Prepare in 
this way seven pieces of white cotton cloth about 6 inches square. 
Wash the cotton three times with water and let it stand under 
water until needed. 

Dissolve 0.1 gram of Congo and 0.1 gram of sodium carbonate 
in 500 cc. of water. Heat the solution to a temperature just 
below boiling, and add pieces of white cotton cloth, woolen cloth, - 
and silk about 6 inches square. Stir occasionally to obtain even 


ee 


DYES AND DYEING 187 


dyeing. At the end of 10 minutes remove the fabrics and wash 
in hot water as long as the dye is removed. Cut the pieces in two, 
and place half of each material in a very dilute solution of hydro- 
chloric acid. Let the samples stay in the air until dry. 


228. Dyeing with an Adjective Dye: Mordants: Malachite 
Green (Sections 530, 541).—Mordant two pieces of boiled out 
cotton cloth (see previous experiment) by allowing them to stand 
for 15 minutes in a cold solution of 0.2 gram of tannic acid in 200 
cc. of water. Fix the tannic acid on one of the pieces by placing 
the cloth without washing into a solution of 0.2 gram of tartar 
emetic in 200 ce. of water, and allowing it to stand for 10 minutes. 

Make a dye bath by dissolving 0.1 gram of malachite green in 
500 cc. of water. Add to the bath a piece of boiled-out cotton 
which has not been mordanted, the piece of cotton mordanted 
wtih tannic acid from which most of the solution has been re- 
moved by pressure, the piece of cotton cloth on which the tannic 


acid was fixed by tartar emetic, a piece of wool, and a piece of 


silk. Dye for 15 minutes at a temperature just below boiling. 
Work the pieces over and over with a rod occasionally to obtain 
even dyeing. 

Wash the dyed material in boiling water as long as color is 
removed. Dry. Compare the appearance of the three pieces of 
cotton cloth. Why is the piece which was treated with tannic 
acid and tartar emetic darker than the one mordanted with tannic 
acid alone? 


229. Dyeing with an Ingrain Color: Primuline (Srction 531). 
—Dye three pieces of boiled-out cotton cloth (see experiment 
227) in a solution of 0.2 gram of primuline and 0.2 gram of sodium 
carbonate in 500 ce. of water, at a temperature just below boiling 
for 15 minutes. Wash the cloth twice in about 500 cc. of water. 

Prepare a diazotizing bath by dissolving 10 cc. of concentrated 
hydrochloric acid in 500 ce. of cold water and then adding 0.2 
gram of sodium nitrite. Place in the bath the three pieces of 
cloth which have been dyed with primuline, and allow them to 
stay 10 minutes. Stir occasionally. Prepare three baths in 
which the diazotized primuline is to be developed. Dissolve 0.1 
gram $-naphthol in 1 ce. of a 10 per cent solution of sodium 
hydroxide, and add 100 ce. of water; dissolve 0.1 gram resorcinol 


188 EXPERIMENTAL ORGANIC CHEMISTRY 


in 2 cc. of the sodium hydroxide solution and add 100 ce. of water; 
dissolve 0.1 gram of phenol in 1 cc. of the sodium hydroxide solu- 
tion and add 100 cc. of water. 

Transfer the cloth from the diazo bath ‘to a beaker containing 
about 500 cc. of water and stir. Put one piece of cloth in each 
of the developing solutions, and allow them to stay 5 minutes. 

Wash the dyed cloth twice with water and dry. 


CHAPTER XXV 


HETEROCYCLIC COMPOUNDS 


230. Formation of Thiophene (Srction 555).—Shake together 
in a test-tube 1 gram of red phosphorus and 2 grams of flowers 
of sulpher. Heat the mixture over a free flame until action 
begins. Prepare some sodium succinate by neutralizing 2 
grams of succinic acid with a strong solution of sodium carbonate 
and evaporating to dryness. Hoop.—Powder the residue and 
grind it with the phosphorus sulphide. Place the mixture in an 
8-inch test-tube which is fitted with a glass tube bent at two right 
angles;the second bend of the tube should pass to the bottom of 
a test-tube placed in a beaker containing ice and concentrated 
hydrochloric acid. Heat under the hood the tube containing the 
mixture of sodium succinate and phosphorus trisulphide as long 
as anything distils. Note whether the oil is lighter or heavier 
than water. 

Add to a drop of the oil a trace of isatin and 1 cc. of concen- 
trated sulphuric acid. ‘Test a sample of commercial benzene and 
one of benzene purified by crystallization from thiophene. 


231. Formation of Furfuraldehyde (Srcrion 557).—Boil a 
small piece of gum arabic in a test-tube with 5 cc. of dilute sul- 
phuric acid. Hold in the vapors escaping from the tube a piece 
of paper which has been moistened with a solution of 2 drops of 
aniline and 2 drops of glacial acetic acid in 2 cc. of water. 


232. Properties of Pyridine (Srctions 560, 561).—(a) Base- 
forming property of pyridine—Dissolve about 1 cc. of pyridine 
in 5 cc. of water and test the solution with litmus paper. 

Add a solution of pyridine to a solution of ferric chloride and to 
one of aluminium chloride. (Kq.) 

(b) Pyridine and mercuric chloride——Add an aqueous solution 
of pyridine to one of mercuric chloride. The crystalline pre- 
cipitate has the composition HgCly.C;H;N. 

189 


190 EXPERIMENTAL ORGANIC CHEMISTRY 


(c) Pyridine and oxidizing agents—Determine whether pyri- 
dine is oxidized by a solution of potassium permanganate, by 
concentrated nitric acid, or by a mixture of potassium bichromate 
and sulphuric acid. | 

(d) Behavior of pyridine as an amine.—Determine whether 
pyridine is a primary, secondary, or tertiary amine. Describe 
in detail the tests applied. 

(e) Pyridine and methyl iodide-——Mix together in a test-tube 
5 drops of pyridine and 5 drops of methyl iodide. Set aside 
and examine after afew hours. (Kq.) 


233. Preparation of Quinoline by Skraup’s Synthesis (Sxc- 
TION 563).—In a 1500 cc. flask place 24 grams of nitrobenzene 
and 38 grams of aniline; add cautiously 100 grams.of pure 
concentrated sulphuric acid, and then, slowly with shaking, 120 
grams of glycerol. Connect the flask with a long reflux water- 
condenser, the inner tube of which has a wide bore. Support 
the flask and condenser by means of clamps. Do not use a gauze 
or bath, but heat the flask directly, cautiously, with a free flame. 
In a short time a vigorous reaction will begin, and a large amount 
of heat is evolved; when this occurs remove the flame. When the 
spontaneous boiling ceases, place a wire-gauze under the flask, 
and heat to boiling for 2 hours. Cool the flask slightly, add about 
100 cc. of water and distil with steam as long as an oil passes over. 
This distillation serves to remove the excess of nitrobenzene. 
Cool the flask under running water, and add a cold solution of 100 
grams of sodium hydroxide in 150 cc. of water. Distil over the 
quinoline with steam. When an oil no longer separates in the 
condenser, stop the distillation. 

The aqueous distillate contains the quinoline formed in the 
reaction and a small amount of aniline. In order to separate the 
latter, advantage is taken of the fact that aniline is converted 
into a diazo compound by nitrous acid, whereas quinoline, being 
a tertiary amine, is not affected by this reagent. When the aque- 
ous solution containing the diazo compound is heated, the latter 
is converted into a phenol. Quinoline can be readily separated 
from phenol by distillation with steam from an alkaline solu- 
tion, in which the phenol is present as the sodium salt and is, 
therefore, non-volatile. To effect this separation treat the aque- 


HETEROCYCLIC COMPOUNDS 191 


ous distillate as follows: Add to the distillate 10 ce. of concen- 
trated sulphuric acid. There should be a small excess of acid 
over that required to dissolve the oil. Next add a few cubic 
centimeters of a solution of sodium nitrite and stir vigorously. 
Continue the addition until the solution smells strongly of the 
oxides of nitrogen. The quinoline is liberated from its salt by 
adding a solution of 40 grams of sodium hydroxide in 50 ce. 
of water. Distil again with steam as long as an oil passes over. 
Separate the oil, dry it with solid potassium hydroxide and dis- 
til. By extracting with ether the aqueous solution, from which 
the quinoline was finally separated, the yield can be slightly 
increased. 

Quinoline boils at 238°. The yield in this preparation is 
about 38 grams. 


ALKALOIDS 


234. General Reactions of Alkaloids (Smction 571).—Dis- 
solve the amount of quinine sulphate that can be held on the 
point of a pen-knife in about 20 cc. of water. Observe the 
appearance of the solution. Add to 2 cc. of the solution, drop by 
drop, a dilute (1 per cent) solution of tannic acid. . Repeat using 
solutions of phosphomolybdic acid, picric acid, iodine in potas- 
sium iodide, and potassium mercuric iodide. The last-named 
solution can be prepared by adding an excess of a solution of 
potassium iodide to a solution of mercuric chloride. 


235. Test for an Alkaloid in Tobacco: Nicotine (Srcrion 
573).—In a small distilling flask boil together one cigarette, 25 
ee. of water, and 2 cc. of dilute sulphuric acid. At the end of 
10 minutes, add an excess of a solution of sodium hydroxide, 
connect the flask with a condenser, and distil over about 10 ce. of 
the solution. Test the distillate by adding to separate portions 
of it, drop by drop, solutions of the following: mercuric chloride, 
tannic acid, iodine in potassium iodide, and potassium mercuric 
iodide. 


CHAPTER XXVI 
PROTEINS 


236. Detection of Nitrogen, Sulphur, and Phosphorus in 
Proteins.—The methods described below illustrate those com- 
monly used in the analysis of proteins. 

(a) Analysis for nitrogen by means of soda-lime.-—Hoov.— 
Heat about 0.1 gram of casein with five times its weight of soda- 
lime in a dry test-tube over a small flame. Observe the odor 
of the gases which escape, and test them with moist litmus paper. 

(b) Analysis for phosphorus and sulphur by fusion with potas- 
stum nitrate—Hoopv.—Fuse together cautiously in a small porce- 
lain crucible about 0.1 gram of casein, 0.2 gram of potassium 
nitrate, and 0.1 gram of anhydrous sodium carbonate. When 
the mixture is colorless, let it cool; then add 10 cc. of water and 
heat to boiling. The fusion has converted the phosphorus into 
sodium phosphate. The acid radical is tested for in the usual 
way. Acidify about 2 cc. of the solution with nitric acid, and 
add a solution of ammonium molybdate. If no precipitate forms, 
warm gently (about 60°) and set aside. A yellow precipitate 
indicates the presence of phosphorus. 

Acidify about 2 cc. of the solution from the fusion mixture, 
which contains a sulphate if sulphur is present, with hydrochloric 
acid, and add a solution of barium chloride. Heat the solu- 
tion to boiling and set aside. Examine the tube for a white 
precipitate. 

(c) Analysis for sulphur by decomposition with sodium hydrox- 
ide.—Boil about 0.1 gram of casein with 5 cc. of a 10 per cent 
solution of sodium hydroxide to which a drop of lead acetate 
solution has been added. If a black precipitate is not evident, 
filter the solution through a paper and observe if a precipitate 
is left on the paper. When proteins containing sulphur are de-, 
composed by sodium hydroxide, sodium sulphide is formed; the 
latter is converted into lead sulphide by lead salts. 

(d) Analysis for nitrogen, phosphorus, and sulphur by fusion 

192 


PROTEINS 193 


with sodium.—Analyze a sample of dried egg-white for nitrogen, 
phosphorus, and sulphur by the method commonly used in the 
qualitative analysis of organic compounds (§58-61, page 39). 


237. Precipitation Reactions of Proteins (Section 586).—The 
protein solution to be used in the following experiments is pre- 
pared as follows: Beat egg-white for a short time to break the 
membranes, and squeeze it through cotton cloth. Mix with 
ten times its volume of water and filter through paper. This 
gives a solution which contains about 1 per cent of protein. 

(a) Strong mineral acids: Heller’s test—Put 2 cc. of egg- 
white in a test-tube; incline the tube, and pour cautiously down 
the side concentrated nitric acid in such a way that the acid 
sinks to the bottom of the tube and two layers are formed. 
Shake the tube. Is the precipitate dissolved? Dilute 2 cc. of the 
ege-white solution with 100 cc. of water, and test 2 cc. of this 
solution as before with nitric acid. Determine whether the pro- 
tein is precipitated from the 1 per cent solution by dilute hy- 
drochloric acid and by dilute acetic acid, and if it is soluble in 
an excess of the acid. 

(b) Salts of the heavy metals —To 2 cc. of egg-white solution 
add 1 drop of a solution of mercuric chloride. For what purpose 
can this reaction be used? 

Test in the same way the effect on the protein of a solution of 
lead acetate, of silver nitrate, and of copper sulphate. To the 
tube containing the precipitate with copper sulphate add 3 to 4 
drops of a solution of sodium hydroxide, dilute, and note the 
color. 

(c) Alkaloidal reagents in acid solutions. Hydroferrocyanic 
acid.—Add to 2 ce. of egg-white solution 5 drops of glacial acetic 
acid and 1 drop of a solution of potassium ferrocyanide. 

Tannic acid.—Add, drop by drop, to 2 cc. of egg-white solu- 
tion a solution of tannic acid. 

Picric acid.—Repeat with a solution of picric acid. 

Potassium mercuric todide——Prepare the reagent by adding 
to a few drops of a solution of mercuric chloride a solution of 
potassium iodide until the precipitate first formed is dissolved. 
Add to 2 ce. of egg-white solution a drop of dilute hydrochloric 


acid and a drop of the reagent. 
13 


194 EXPERIMENTAL ORGANIC CHEMISTRY 


Bromine.—Add bromine-water to 2 cc. of the egg-white solu- 
tion until a permanent yellow color is formed. 

(d) Coagulation by alcohol—Add to 5 cc. of the egg-white 
solution twice its volume of alcohol. Set aside until the next 
exercise. Filter and test the solubility of the precipitate in 
water. To do this, wash the precipitate with water, and test 
the solution for protein. 

(e) Heat coagulation—Heat 2 cc. of the egg-white solution 
to boiling. To 2 cc. of the egg-white solution add 1 or 2 drops 
of a 0.5 per cent solution of acetic acid, and heat to boiling. 
Compare the results in the two cases (see note below). 

Determine the temperature of coagulation of egg-white as 
‘follows: Add to 5 cc. of the protein solution 5 drops of a 0.5 per 
cent solution of acetic acid. The mixture should be faintly acid 
to delicate litmus paper. Put a thermometer in the solution, 
and place the test-tube in cold water in a beaker; heat the water 
and determine the temperature at which the solution clouds and 
when the precipitate separates in flocks. Stir from time to time 
with the thermometer. 

Notrs.—(a) Heller’s reaction is a very delicate test for most proteins; 
peptones are not precipitated by nitric acid. 

(c) A reaction with potassium ferrocyanide takes place only in acid solu- 
tion; neutral salts interfere to some extent with the reaction. Peptones 
are not precipitated by hydroferrocyanic acid. 

(d) Alcohol precipitates proteins unchanged, but on standing the latter 
are converted into a form which is insoluble in water. 

(e) Egg-white is faintly alkaline. Complete precipitation takes place 
only in faintly acid solution. ‘The temperature at which. coagulation takes 
place depends to a large extent on the amount of acid and of salts present. 


238. Color Reactions of Proteins.—(a) Biuret reaction —Add 
to 2 ce. of egg-white solution 2 cc. of a 10 per cent solution of 
sodium hydroxide and 2 drops of a 1 per cent solution of copper 
sulphate. 

(b) Xanthoproteic reaction —To 2 cc. of the egg-white solution 
add 5 drops of concentrated nitric acid and heat to boiling. 
Note the change in color. Cool the solution and make it alkaline 
with ammonia or sodium hydroxide. 

(c) Millon’s reaction.—To 2 cc. of the egg-white solution add 
5 drops of Millon’s reagent. Is a precipitate formed? Heat to 
boiling. 


PROTEINS 195 


(d) Molisch reaction—Add to 2 cc. of egg-white solution 
3 drops of a solution of a-naphthol in chloroform; shake and 
pour cautiously down the side of the test-tube concentrated 
sulphuric acid so that two layers are formed. If no color is 
produced, put the tube aside and examine in a few minutes. 

(e) Sulphur reaction—Add 1 drop of a solution of lead ace- 
tate to 2 cc. of the egg-white solution and then a dilute solution 
of sodium hydroxide until the precipitate is dissolved. Heat to 
boiling. 
~(f) Hopkins-Cole reaction—Add to 2 cc. of the egg-white 
solution 5 drops of a solution of glyoxylic acid (see Appendix). 
Pour down the side of the tube concentrated sulphuric acid so 
that two layers are formed. If no color develops examine the 
tube in a few minutes. 


Notrs.—(a) Excess of copper sulphate must be avoided in making the 
biuret test, since the color of the salt prevents the recognition of the color 
produced in the reaction. The presence of ammonium salts interferes with 
the test. In applying the reaction to solutions containing these salts a 
large excess of sodium hydroxide must be present. Compounds which give 
the biuret test must contain at least two —CO—-NH— groups. The color 
formed in the reaction varies in shade with the complexity of the molecules. 

(6) The color is produced as the result of the formation of nitro-derivatives 
of the compounds which contain a benzene ring, for example, tyrosine. 

(c) The color produced in Millon’s test is given by derivatives of benzene 
in which a hydrogen in the ring has been replaced by ahydroxyl group. The 
reaction serves as a test for the presence of tyrosine. 

(d) If the Molisch test is positive, a carbohydrate is present in the protein 
molecule. 

(e) If sulphur is present a black precipitate or brown coloration is pro- 
duced. If the result is in doubt the solution should be filtered and the paper 
examined. The precipitate, which is lead sulphide, is formed as the result 
of the decomposition of the cystine by the alkali. 

(f) The color produced is due to the formation of a compound from the 
glyoxylic acid in the reagent and the tryptophane in the protein. A similar 
color is produced when sulphuric acid is added to a protein solution in the 
presence of a trace of formaldehyde. The reaction is used as a test for 
formaldehyde in milk. 


239. Study of the Composition of Gelatin and of Wool.— 
Apply the precipitation and color reaction of proteins to a solu- 
tion of gelatin made by dissolving 1 gram of the substance in 100 
ec. of hot water. Cool the solution before it is used. State what 


196 EXPERIMENTAL ORGANIC CHEMISTRY 


conclusion can be drawn from the results as to the presence or 
absence of certain amino-acids in gelatin. 
Apply the color tests to a sample of wool. 


240. Separation of Proteins by Salting Out (Section 580).— 
(a) Separation of a globulin from an albumin by means of sodium 
chloride.—Add to 10 ce. of the egg-white solution finely powdered 
sodium chloride until the solution is saturated and a slight residue 
of salt is obtained (3.6 grams for each 10 ce. of solution). The 
globulin is precipitated. Filter the solution; add to the filtrate 
2 to 3 drops of 0.5 per cent acetic acid, and heat to boiling. The 
albumin which was in solution is coagulated. 

(b) Separation of a globulin from an albumin by means of am- 
monium sulphate—Prepare a saturated solution of ammonium 
sulphate by dissolving 8 grams of the salt in 10 cc. of water. 
Add 10 ce. of this solution to 10 cc. of egg-white solution. In 
this way the latter solution is one-half saturated with ammonium 
sulphate, and the globulin is precipitated. Filter, and to one- 
half of the filtrate add 2 drops of a 0.5 per cent solution of acetic 
acid and boil. The albumin is coagulated. Saturate the other 
half with solid ammonium sulphate; the albumin is precipitated. 
Filter, and test the filtrate as before for protein. 


241. Products of the Hydrolysis of Proteins.—(a) Meta- 
proteins.—In a test-tube place 10 cc. of the egg-white solution 
and 1 cc. of a 10 per cent solution of sodium hydroxide. In a 
second tube place 10 ec. of the egg-white solution and 1 ce. of 
concentrated hydrochloric acid. Place the tubes in a beaker 
containing about 300 cc. of water at 50°, and allow them to stand 
from 15 to 20 minutes. The temperature should not fall below 
40°. The protein is partly converted into alkali-albumin and 
into acid-albumin. 

Boil 2 cc. of the solution in each tube. Is protein precipi- 
tated? Add to 2 cc. of the alkali albumin a drop of dilute 
hydrochloric acid. Is the precipitate soluble in dilute alkali? 
Add to 2 ee. of the alkali albumin a drop of dilute hydrochloric 
acid; heat to boiling. Is the precipitate soluble in dilute alkali 
as before? Explain. Add to 2 cc. of the acid albumin a drop of 
dilute alkali. Is the precipitate soluble in dilute acetic acid? 
Add to 2 cc. of the solution of alkali albumin an equal volume of 


PROTEINS 197 


a saturated ammonium sulphate solution. Is the protein 
precipitated? 

(b) Proteoses and peptones.—Stir 2 grams of Witte’s pep- 
tone with 40 cc. of cold water, and filter from the small insoluble 
residue. 

Add to 2 cc. of the solution 2 to 3 drops of 0.5 per cent solu- 
_tion of acetic acid and boil. Are the proteins coagulated? 


242. Separation of Proteoses and Peptones.—Saturate 20 
ce. of the solution prepared in experiment 241b above with 
ammonium sulphate (16 grams). Filter. Savethe filtrate which 
contains the peptones. Place the filter-paper containing the 
precipitate in a beaker, and heat it with 25 ce. of water. Filter. 
This filtrate contains the proteoses. Apply to the solution of 
the peptones and to the solution of the proteoses the precipita- 
tion and color reactions given above. Compare the results in 
the two cases. In making the biuret test when ammonium salts 
are present, a large excess of alkali must be added; add astrong 
- (1 to 1) solution of sodium hydroxide or about 10 cc. of a 10 
per cent solution to 2 cc. of the solution to be tested. 


243. The Proteins of Wheat (Srmction 590).—(a) Protein 
soluble in water (leucosin)—Shake up about 1 gram of bread 
- flour with 10 cc. of water, filter, and determine whether the 
filtrate contains protein by applying three or four tests. 

(b) Alcohol-soluble protein (gliadin) —Add 25 cc. of water to 

75 ce. of alcohol. Pour the mixture onto about 20 grams of 
bread flour. Stir occasionally during half an hour. Filter, and 
evaporate the filtrate to dryness. Observe the properties of the 
dried protein. Is it brittle? Moisten it with water and after 
a few minutes note its properties. Is it elastic? Prove that it 
is a protein by applying a number of tests. 
- (ce) Separation of gluten—Gluten is a mixture of glutenin 
and gliadin. In a porcelain dish mix 50 grams of bread flour 
with enough water to make a stiff dough (about 25 cc.). Let the 
mixture stand for half an hour. Add about 100 cc. of water and 
work the dough, keeping it in the form of a ball. The starch 
passes into suspension in the water. Pour off the water, and 
add fresh water from time to time until all the starch is re- 
moved. Note the properties of the gluten. 


198 EXPERIMENTAL ORGANIC CHEMISTRY 


The two proteins present can be separated by extracting the 
gliadin with 75 per cent alcohol. This is a tedious process. 
Grind a small part of the gluten in a mortar repeatedly with 10 
ec. portions of 75 per cent alcohol. Finally heat the residue with 
some of the alcohol on the steam-bath. When all the gliadin has 
been removed the protein is no longer elastic. Dissolve the glu- 
tenin in dilute sodium hydroxide and apply a few of the protein 
tests. 


Notre.— Wheat contains the following proteins: Soluble in water, leucosin, 
about 0.4 per cent, and a proteose, about 0.3 per cent; soluble in 10 per 
cent sodium chloride, edestin, about 0,6 per cent; soluble in 75 per cent 
alcohol, gliadin, about 4.3 per cent; insoluble in neutral solvents, glutenin 
from 4.0 to 4.5 per cent. 


244, Isolation of a Crystalline Protein: Edestin from Hemp 
Seed.—Grind in a mortar 25 grams of hemp seed; add the seed in 
small quantities at a time, and see that each seed is crushed. 
Dissolve 28 grams of sodium chloride in 700 ec. of water (4 per 
cent solution of sodium chloride) and heat to 60°. Add the hemp 
seed and stir frequently during 15 minutes. The temperature 
of the solution should be kept between 58° and 60° during the 
extraction of the protein. This can be accomplished by placing 
a very small flame under the beaker. If the temperature rises 
above 60°, the flame should be removed. Filter into a dry 
beaker through a large hot water funnel containing water at 60°. 
Cover the funnel with a watch-glass to prevent loss in heat from 
the solution. Receive the first part of the filtrate in a small 
beaker and return it to the funnel. Set the filtrate aside to cool 
slowly. When the solution is cold, decant off most of the liquid 
carefully and filter off the solid. Place a little of the suspended 
solid on a glass slide, cover, and’examine under a microscope. 
Sketch the crystals. If crystals have not separated from the 
solution before the end of the laboratory period, leave the solu- 
tion in a cool place. Test the edestin crystals by applying the 
following reactions: xanthoproteic, biuret, Hopkins-Cole, Mil- 
lon, sulphur. Shake up some of the protein with 20 cc. of a 
10 per cent solution of sodium chloride. Filter through a dry 
paper into a dry test-tube. If the first part of the filtrate is 
cloudy return it to the funnel. Pour some of the clear filtrate 
into water. Determine whether the protein is coagulated by 


PROTEINS 199 


heat, and whether it is salted out by sodium chloride and by 
ammonium sulphate. 

Norre.—During the extraction of edestins it is necessary to avoid a 
high temperature in order to prevent the coagulation of the protein. 

245. Isolation of Casein from Milk (Srction 596).—To 50 ce. 
of milk add 150 cc. of water and heat the mixture to 30°. Add 
dilute acetic acid, drop by drop, as long as a precipitate is formed 
(about 1 cc. of a 10 per cent solution). Stir vigorously. It is 
necessary to avoid an excess of acid, since the latter dissolves 
some of the protein. Filter. During the filtration test small 
portions of the filtrate for protein by three or four color reactions. 
Heat 10 ce. of the filtrate to boiling. What protein is pre- 
cipitated? Filter this off, and test the filtrate for a sugar 
with Fehling’s solution, and for a phosphate with ammonium 
molybdate. 

Wash the precipitate of casein with 50 cc. of water; press out 
as much water as possible, and then wash the precipitate twice 
with 20 cc. of alcohol. Squeeze out the alcohol, and press 
the casein between a number of pieces of filter-paper. Break 
up the casein and let it dry in the air. Determine whether it is 
soluble in water. To do this, grind in a mortar a little of the 
solid with 10 cc. of water, filter, and test the filtrate for a protein 
with concentrated nitric acid. If the filtrate is not clear, refilter 
it through two filter-papers. Determine if casein is soluble in 
sodium carbonate solution. Proceed as before; acidify the fil- 
trate and test it for a protein. 

Put into a mortar 10 cc. of water and 3 or 4 drops of a dilute 
solution of sodium hydroxide. ‘Test the solution with red litmus 
paper. Next add some casein and grind it thoroughly in the 
alkaline solution. Test the solution again with red litmus 
paper. What conclusion can you draw in regard to the chemical 
nature of casein. Filter the solution through a wet filter-paper, 
and add to the filtrate a few drops of a solution of calcium 
chloride. Explain. 


TEXTILE FIBERS 
246. Appearance of Fibers.—Examine under a microscope a 


fiber of each of the following: silk, wool, cotton, mercerized 
cotton, and linen. 


200 EXPERIMENTAL ORGANIC CHEMISTRY 


247. Properties of Wool, Silk, and Cotton.—(a) Effect of 
burning.—Burn a thread of wool, of silk, and of cotton. Notice 
the odor produced during the burning. Explain. At the end of 
a few seconds blow out the flame and observe the appearance of 
the charred residue. 

(b) Action of sodium hydroxide—For this and the following 
experiments use pieces of the material about 1 inch square. 
Place in a test-tube a piece of cotton, a piece of silk, and a piece 
of wool; add about 10 cc. of a 10 per cent solution of sodium hy- 
droxide. Heat the solution to such a temperature that the tube 
can just be held in the hand (about 65°); shake, and keep the tube 
hot by heating it occasionally until the wool dissolves. Heat to 
boiling for some minutes and note the effect. Explain the cause 
of the difference in behavior of the animal and vegetable fibers. 

(c) Action of concentrated hydrochloric acid.—Shake pieces of 
cotton, silk, and wool with about 10 cc. of cold concentrated 
hydrochloric acid. One of the pieces should dissolve. 

Place a piece of cotton and a piece of wool in a mixture of 1 ce. 
of concentrated hydrochloric acid and 5 ce. of water. Press out 
as much of the solution as possible. Set aside to dry and examine 
at the next exercise. Try to tear the material. 

(d) Examination of wool and of silk for sulphur—Add a few 
drops of a solution of lead acetate to about 20 cc. of a 10 per cent 
solution of sodium hydroxide. Divide the solution into two 
portions. In one dissolve a piece of wool and in the other a 
piece of silk. 

(e) Action of Miullon’s reagent (Srction 586).—Miaillon’s re- 
agent is prepared by using the substances in the following pro- 
portions: One gram of mercury is dissolved in 2 cc. of hot con-_ 
centrated nitric acid and the resulting solution diluted with 3 ce. 
of water. 

Dilute 2 cc. of the reagent with 10 cc. of water, add to the solu- 
tion pieces of cotton, silk, and wool, and heat to boiling. 

(f) Test of textile fabrics—Test the samples submitted, mak- 
ing use of the results obtained in (a), (b), (c), (d), and (e) above. 
The samples may consist of cotton, silk, or wool, or mixtures 
of any two of the fibers. It is a common practice to make 
fabrics in which the threads running in one direction are of 
one material, and those running in another are of a different 


PROTEINS 201 


material. Designs in pure silk are often woven into a fabric 
made of mercerized cotton. These designs can be readily 
developed by warming a sample of the material with Millon’s 
reagent. 


CHAPTER XXVII 
THE IDENTIFICATION OF ORGANIC COMPOUNDS 


248. Throughout the laboratory course outlined in the pre- 
vious chapters, the typical reactions of a number of important 
classes of compounds have been illustrated by experiments. 
These reactions are made use of in the identification of organic 
compounds. Practice in such identifications is of great edu- 
cational value, as it requires continuous thought on the part of 
the student, is an excellent review of many facts which have 
been learned, and has a practical significance. 

No set analytical scheme is available as is the case in inor- 
ganic qualitative analysis. Thesubject is more complicated than 
the latter, and each compound requires special study. By the 
application of a few simple tests it is often possible to determine 
to what class a compound belongs. In order to facilitate the 
work the student should prepare a table which summarizes the 
behavior of certain typical compounds with a few important 
reagents. To do this proceed as follows: Divide a large sheet 
of paper into squares by drawing on it twenty horizontal and 
fifteen vertical lines. Place in the first vertical column on the 
left side of the paper the names of the following important 
classes of compounds, using a square for each class: paraffin 
hydrocarbons, unsaturated hydrocarbons, aromatic hydrocar- 
bons, alcohols, phenols, acids, ethers, anhydrides, esters, alde- 
hydes, ketones, amines, amides, nitriles, nitro compounds, halo- 
gen compounds, sulphonic acids, carbohydrates. In the squares 
that form the upper horizontal column write the following: water, 
cold solution of sodium hydroxide, hot solution of sodium 
hydroxide, solution of sodium carbonate, dilute hydrochloric 
acid, cold concentrated sulphuric acid, acetyl chloride, sodium, 
bromine, influence of substituents, influence of aromatic group, 
special reactions, and remarks. State briefly, as far as possible, 
in the appropriate squares, the behavior of the several classes of 

202 


IDENTIFICATION OF ORGANIC COMPOUNDS 203 


compounds with the reagents listed. It will take time and study 
to do this satisfactorily. The following references to the sections 
in the text-book and to the laboratory experiments will be of 
value in getting together the facts to be incorporated into the 
table. It is important that any notes under the experiments 
referred to should be read: paraffin hydrocarbons, 26, 27, and 
experiment 70, page 46; unsaturated hydrocarbons, 35, 43, and 
experiments 74 and 75, page 50; aromatic hydrocarbons, 352, 
and experiments 164d to h, page 129; alcohols, 67, 61, and ex- 
periment 79, page 55; phenols, 456, and experiments 197, 198, 
page 162; acids, 97, and experiments 90, 91, page 63; ethers, 
119, and experiment 96, page 71; anhydrides, 123, and experi- 
ment 98, page 73; esters, 139, and experiment 103, page 77; 
aldehydes, 151, and experiment 108, page 83; ketones, 158, and 
experiment 111, page 84; amines, 170, 423, and experiments 
113, 183, 184, 185, pages 86,149,151; amides, 186, and experi- 
ment 116, page 89; nitriles, 197, and experiment 127, page 94; 
alkyl halides, 206, and experiment 132, page 98; acyl halides, 
223, and experiment 139, page 105; aryl halides, 402, and experi- 
ment 180, page 144; carbohydrates, 313, and experiments 148, 
152, 156, pages 115, 119, 124; nitro compounds, 391, and experi- 
ment 171, page 136; sulphonic acids, 399, and experiment 174, 
page 140. 


249. The properties of the members of any class are in general 
like those illustrated in the case of the simpler members, which 
have been studied by the student. It is important to remember, 
however, that increase in molecular weight generally leads to 
decreased solubility and chemical activity. For example, the 
anhydrides with low molecular weight of the homologues of 
acetic acid react promptly with water, whereas those of high 
molecular weight must be. heated with water for some time to 
bring about hydrolysis. It is also important to remember that 
the presence of a second group in a compound often modifies 
the properties which a characteristic group gives to it; for ex- 
ample, monatomic phenols are insoluble in dilute hydrochloric — 
acid, but aminophenol dissolves in this reagent on account of 
the presence of the amino group. 

Before beginning to identify an unknown compound the student 


204 EXPERIMENTAL ORGANIC CHEMISTRY 


should study Srcrions 328 to 331 inclusive, and solve problem 
2 at the end of Chapter XVII in the text-book. The work 
should be done carefully with small amounts of the substance 
to be studied. About 10 grams of a pure compound is ordinarily 
enough for complete identification, including the preparation of 
a derivative and the determination of its physical properties. 
Solubilities can be determined with a crystal or a single drop. 
The first substances given to the student should be practically 
pure. 

The work is begun by testing the purity of the sample to be 
identified. If it is a liquid the substance should be distilled very 
carefully from a small flask (§44, page 29). If the substance 
is a solid its melting-point should be determined. Record the 
result obtained, as it is to be used in the final identification. If 
the substance is impure it should be purified before being studied 
further. Burn some of the substance (experiments 164d, note, 
and 180b, pages 130, 144,) and determine if possible if it 
is an aromatic compound (experiment 164e and f, note). Next 
make a qualitative analysis (§57—-61, pages 38, 41). Ifany element 
other than carbon, hydrogen, and oxygen is found, it is well to 
make tests to discover in what group the element is present. 
Study next the behavior of the substance with the reagents 
given in the table prepared as described above, and test with 
Tollen’s and Schiff’s reagent. If the substance appears to be a 
carbohydrate, apply the Molisch test. 


250. When the class or classes to which the compound belongs 
and the melting-point or boiling-point have been determined, 
consult large texts, or other reference books on organic chemistry, 
which contain tables or lists of compounds with their physical 
properties. Such books as Richter, Organic Chemistry; Beil- 
stein, Handbuch der organischen Chemie; Mulliken, Identi- 
fication of Pure Organic Compounds; Chemiker Kalender; 
Meyer and Jacobson, Lehrbuch der organischen Chemie; and 
Van Nostrand’s Chemical Annual are useful. Take into con- 
sideration compounds the melting-points of which le within 
about four degrees on either side of the point observed. Such a 
range is necessary as the melting-points and boiling-points 
recorded are at times far from accurate. When one or more 


IDENTIFICATION OF ORGANIC COMPOUNDS 205 


compounds are found the descriptions of which fit those of the 
substance under study, find out what derivative which possesses 
a satisfactory melting-point or boiling-point can be readily made. 
It is best to prepare a solid whenever possible, since in this case 
much smaller amounts of substance can be used. Look up the . 
properties of this derivative and its method of preparation, and 
convert about 1 gram of the substance to be identified into the 
the derivative if the latter is a solid; if it is a liquid more will be 
required. Before making the preparation read carefully pages 
28 to 31, where the special technique of handling small quanti- 
ties is described. Determine the melting-point or boiling-point 
of the compound prepared; if this agrees with the number as 
given, the identification of the original substance may be con- 
sidered satisfactory. 

In the case of certain compounds it is difficult to transform 
them into other substances when only a small amount is avail- 
able. In this case, if the compound is a liquid, it is often con- 
venient to determine its specific gravity ($56, page 37) as an 
aid in its identification. At times both the melting-point and 
the boiling-point of a substance can be determined; these two 
constants often will serve to identify acompound. For theiden- 
tification of a substance it is necessary to have at least two phys- 
ical constants agree with those which have been recorded; these 
may be constants of the substance itself, or one may be a constant 
of the substance and one of a compound into which it has been 
converted. Reliance on one constant often leads to mistakes. 
For example, o-chlortoluene boils at 154° and m-chlortoluene at 
156°. It would be very difficult to identify either substance by 
a determination of its boiling-point alone. The identification is 
readily accomplished, however, by converting the compounds 
into the corresponding benzoic acids; o-chlorbenzoic acid melts 
at 137° and m-chlorbenzoic acid at 153°. 


251. In the following list, the derivative which can be conven- 
iently prepared, in most cases, from the several classes of com- 
pounds is given. In some cases specific gravity determinations 
are made, although it is preferable to convert the compound 
into another substance if possible: paraffin hydrocarbons, specific 
gravity; unsaturated hydrocarbons, addition-products with bro- 


206 EXPERIMENTAL ORGANIC CHEMISTRY 


mine or hydriodic acid; aromatic hydrocarbons, solid nitrocom- 
pounds (experiment 172, note, page 138), or addition-products 
with picric acid (experiment 169c, page 133); alcohols, special 
tests or solid esters of aromatic acids; phenols, bromine substi- 
tution-products; monobasic fatty acids, solid anilides (experiment 
91c, page 64), or esters; polybasic acids, characteristic salts; 
aromatic acids, amides (experiment 202, page 166) or nitro- 
derivatives; ethers, specific gravity or conversion into iodides 
(experiment 967, page 72); aromatic ethers, as above, or nitro- 
derivatives; fatty anhydrides, anilides (experiment 98e, page 
74); aromatic anhydrides, change to acids; esters, hydrolysis 
and identification of the acid or alcohol formed; fatty aldehydes, 
specific tests; aromatic aldehydes, nitroderivatives or special 
tests; ketones, oximes (experiment 210, page 172), or special 
tests (experiment 111f, page 85); fatty amines, salts with 
hydrochloric acid; aromatic amines, acetyl derivatives or special 
tests; amides, change to acids; nitriles, change to acids; nitro 
compounds, further nitration or reduction to amines; sulphonic 
acids, amides; carbohydrates, special tests, osazones, behavior 
with Fehling’s solution, etc. 


252. Study of Mixtures.—(See Section 331).—The mixture 
should be treated in turn with twice its volume of water, dilute 
hydrochloric acid, dilute sodium’ hydroxide, and concentrated 
sulphuric acid. When sulphuric acid is used care must be taken 
to keep the mixture cold. If the mixture is a liquid it should be 
treated with solvents in a graduated cylinder. The volume of 
the liquid should be noted before and after shaking with the 
solvents; in this way it can be easily seen whether any of the mix- 
ture dissolves. If this occurs the mixture should be treated 
with small quantities of the solvent as long as any of its dissolves. 
The several solutions should be examined separately. The water 
solution should be carefully distilled. It is tested first with lit- 
mus paper to determine whether an acid or an amine is present. 
If an acid is present the solution should be neutralized with 
sodium hydroxide before distillation. The acid will remain in 
the flask as a sodium salt and other volatile substances will pass 
over. The boiling-point should be carefully noted during the 
whole distillation. If there is evidence of the presence of any- 


IDENTIFICATION OF ORGANIC COMPOUNDS 207 


thing in solution, tests should be applied to the distillate for the 
classes of substances soluble in water. 

The extract obtained by treatment with acid should be ren- 
dered alkaline. If a basic substance has been removed it will be 
precipitated; this should be separated and tested. 

The extract obtained with sodium hydroxide is next treated 
with dilute hydrochloric acid. If an acid or phenol is present 
it will be precipitated, and is examined. - 

The concentrated sulphuric acid solution is poured very care- 
fully onto twice its volume of cracked ice. Any substance which 
is precipitated is washed with a little water, separated, and ex- 
amined. If two substances which belong to the same class of 
compounds are present in a mixture, it is usually necessary to 
separate them by fractional distillation. 

A full record of all tests used should be placed in the note- 
book. The observed physical properties (melting-point, boiling- 
point or specific gravity) of the substance and of the compound 
prepared from it should be given together with the physical 
properties as recorded in the reference books. 


APPENDIX | 


ScHIFF’s’ REAGENT 


Dissolve about 0.2 gram of rosaniline in a small amount of 
boiling water. Cool and add 15 cc. of a saturated solution of 
sulphur dioxide in water, and allow the mixture to stand several 
hours until it becomes colorless or pale yellow; then dilute to 
200 cc. with water. The reagent should be kept in a weil-stop- 
pered bottle of dark glass. 


TOLLEN’S REAGENT 


Make an ammoniacal solution of silver nitrate by dissolving 
10 grams of the salt in 100 cc. of a solution of ammonia prepared 
by mixing equal volumes of concentrated ammonia (sp. gr. 0.9) 
and water. When ready to make a test, mix a portion of this 
solution with an equal volume of a 10 per cent aqueous solution 
of sodium hydroxide. The test should be made in the cold. 
The sodium hydroxide should be added immediately before 
use; on standing or on heating, the mixture so prepared deposits 
a black explosive precipitate. | 


FEHLING’S SOLUTION 


Dissolve 34.64 grams of pure crystalline copper sulphate in 
distilled water, and dilute to 500 cc. Dissolve 70 grams of 
sodium hydroxide and 180 grams of pure Rochelle salt in 400 cc. 
of water, and dilute to 500 cc. The solutions should be kept in 
separate bottles until used. Fehling’s solution is made by mixing 
equal volumes of the two solutions. A solution prepared in this 
way is of such a strength that 1 cc. of it will oxidize 0.005 gram 
of dextrose. 

208. 


APPENDIX 209 


Mituon’s REAGENT 


Dissolve 10 grams of mercury in 20 cc. of hot concentrated 
nitric acid, and dilute the resulting solution with 30 cc. of water. 


Hoprpxkins-CoLeé REAGENT 


In a large flask place 10 grams of powdered magnesium, cover 
the latter with distilled water, and add slowly, keeping the mix- 
ture cold, 250 cc. of a cold saturated solution of oxalic acid. 
When the reaction is complete, filter, make the filtrate slightly 
acid with acetic acid, and dilute to 1000 cc. with distilled water. 


PREPARATION OF HyDROBROMIC ACID 


The constant-boiling mixture of hydrobromic acid and water 
can be conveniently used to prepare alkyl bromides. The acid 
boils at 126°, contains about 47.5 per cent of hydrogen bromide, 
and has a specific gravity of about 1.48. 

The acid can be prepared from potassium bromide or from 
bromine. 

(a) From potassium bromide.—In a 250 cc. distilling flask 
pour slowly into 85 cc. of water 98 grams of pure concentrated 
sulphuric acid. To the mixture add 119 grams of powdered 
potassium bromide and distil slowly, using a water-jacketed 
condenser. Collect the fraction boiling at 125°-126°. The yield 
is 85 to 90 per cent of the theoretical. 

(b) From bromine.—In a 200 ce. distilling flask place 162 cc. 
of water and 10 grams of red phosphorus; cover the side-arm of 
the condenser with a cork (Fig. 14, page 25), connect the flask 
with a return condenser, and place itin a water-bath so that itis 
completely covered with cold water. Put 40 cc. of bromine in a 
small separatory funnel, and support the latter in the condenser 
at the top. Allow the bromine to flow into the flask slowly, 
drop by drop. When all the bromine has been added, support 
the flask on a wire gauze, connect it with a condenser and distil. 
Collect the part which boils at 125°-126°. The yield is about 
95 per cent of the theoretical. 


14 


210 EXPERIMENTAL ORGANIC CHEMISTRY 


PREPARATION OF HyprRiopic ACID 


The constant-boiling aqueous solution of hydriodic acid can be 
conveniently used for the preparation of alkyl iodides. The solu- 
tion contains about 57 per cent of hydriodic acid, boils at 127°, 
and has the specific gravity of 1.68 to 1.70. The exact composi- 
tion varies with the pressure at which the acid is distilled. The 
solution is prepared as follows: In a 100 ce. distilling flask place 
65 ce. of water and 70 grams of iodine. Put the flask in a water- 
bath containing cold water, and force it down so that the whole 
bulb of the flask is submerged. Hold the flask in place by means 
of a clamp and ring-stand. Add 6.5 grams of red phosphorus. 
Let the flask stand for about 5 minutes. Support it on a wire 
gauze, connect with a condenser and distil. Collect what boils 
at 126°-127°. The yield is about 95 per cent of the theoretical. 


A 


Acetaldehyde, 82-84 
_ Acetamide, 88-90 
Acetanilide, 64, 74 
Acetic acid, glacial, 63 
preparation of, 62 
properties of, 63 
tests for, 64 
Acetic anhydride, 73 
Acetoacetic ester, 110 
_ synthesis, 111, 112 
Acetone, 84 
identification of, 85 
Acetyl chloride, 105 
Acetylene, 51 
Acids, aromatic, 165 
fatty, 61 
Acyl chlorides, 105 
Albumin, 196 
Alcohol, see ethyl alcohol 
Alcohols, 53 
aromatic, 160 
Aldehyde, see acetaldehyde 
Aldehydes, 81 
aromatic, 170 
Alkaloidal reagents, 193 
Alkaloids, 191 
Allyl alcohol, preparation of, 58 
properties of, 59 
Amides, 88 
Amines, 86 
aromatic, 148 
Aminoazobenzene, 156 
Amylene, 50 
Analysis, 202 
qualitative, 38 
Anhydrides, 73° 
Aniline, formation of, 136 
preparation of, 148 
properties of, 149-151 


INDEX 


Anisol, 164 
Anthraquinone, 174 
Azo dye, 183 


B 


Barium ethyl sulphate, 75 
Baumann and Schotten reaction, 
60 
Beckmann’s rearrangement, 172 
Benzaldehyde, properties of, 170 
Benzalphenylhydrazone, 159 
Benzamide, 166 
Benzanilide, 165 
Benzene, preparation of, 128 
properties of, 128-130 
Benzenesulphonamide, 141 _ 
Benzenesulphonie acid, 138 
Benzenesulphony] chloride, 140, 152 
Benzoic acid, detection in foods, 
180 
identification of, 165 
preparation of, 165 
Benzophenone, 170 
from diphenylmethane, 132 
Benzophenoneoxime, 172 
Benzyl alcohol, 160 
Biuret, 91 
Boiling-points, determination of, 35 
Bone-black, use of, 8 
Bromine, test for, 41 
Brombenzene, 143 
Bumping, prevention of, 27 
Butter, saponification of, 79 
Butyric acid, 112 


C 
Caffeine, from tea, 127 


Calcium oxalate, 68 _ 
Carbohydrates, 114 


212 


Carbon disulphide, test for, 129 
Casein, 199 
Cellulose, 122, 123 

acetate, 123 

nitrate, 123 
Chloral, 113 
Chlorine, test for, 40 
Chloroform, 101, 102 
Cinnamie acid, 167 
Citrie acid, 109, 110 
Cloves, oil of, 176 
Coagulation of proteins, 194 
Colloidal solutions, 119 
Condensers, reflux, 25 
Congo red, 186 
Cotton, 200 
Crystallization, 3, 28 
Cyanides, 93 

alkyl, 94 

test for, 92 
Cyanogen, 92 


D 


Dextrin, 122 
Dextrosazone, 114 
Dextrose, 114 
Dialysis, 119 
Diazo compounds, 153 
Diazoaminobenzene, 156 
Dibenzalacetone, 85 
Dibrombenzene, p, 144 
Digestion, salivary, 121 
Di-isoamyl, 45 
Dimethylaniline, 151 
Dimethyl terephthalate, 168 
Dinitrobenzene, m, 137 
Diphenyl-carbinol, 161 
-ethycarbinol, 161 
-methane, 132 
Distillation, 8, 29 
fractional, 11, 42 


under diminished pressure, 14 


with steam, 18 
Drying agents, 24 
Dyeing, 186 
Dyes, 183 


INDEX 


1) 


Edestin, 198 
Emulsification, 79 
EKosin, 186 
Esters, 75 
properties of, 77 
Ethane, 45 
Ether, absolute, 70 
preparation of, 69 
properties of, 71 
Ethers, 69 
properties of, 71, 72 
Ethyl acetate, preparation of, 76 
properties of, 77 
Ethylacetoacetic ester, 111, 112 
Ethyl alcohol, absolute, 57 
tests for, 57 
preparation of, 53 
properties of, 55 
Ethyl-benzene, 130 
bromide, 97—99 
iodide, 99, 100 
sulphuric acid, 75 
Ethylene, 49, 50 
bromide, 103, 104 
Eugenol, 176 
Extraction, 20, 30 


F 


Fat, saponification of, 64, 79 
Fats, 78 

Fehling’s solution, 208 
Fermentation, 53, 116 
Ferric citrate, 110 
Flash-point, 47 

Flour, composition of, 197 
Fluorescein, 185 
Formaldehyde, 81 

Formic acid, 61 
Furfuraldehyde, 189 


G 


Gasoline, 46, 47 
Gelatin, 180 
composition of, 195 


INDEX 


Gliadin, 197 
Globulin, 196 
Gluten, 197 
Glycerol, 66 

properties of, 59 
Glyceryl tribenzoate, 60 
Grignard reaction, 161 


H 


Halogen compounds, 96 
aromatic, 148, 144, 145 
Halogens, test for, 40 
Heller’s test, 193 
Hemp seed, 198 
Heterocyclic compounds, 189 
Hexaphenylethane, 133 
Hopkins-Cole reaction, 195 
reagent, 209 
Hydriodic acid, preparation of, 210 
Hydrobenzamide, 170 
Hydrobromic acid, preparation of, 
209 
Hydrocarbons, aromatic, 128 
saturated, 42 
unsaturated, 49, 50, 51 
Hydroxy acids, test for, 107 


I 


Identification of compounds, 202 
Jodine, test for, 41 
Iodobenzene, 154 
Iodoform test, 57 
Ingrain colors, 187 
Ink, 181 
Isoamyl, acetate, 78 
bromide, 100 
ethyl ether, 72 
Isocyanides, 95 


K 


Kerosene, 46, 47 
Ketones, 84 


L 


Lactic acid, 106 
Lactose, 117, 118 


213 


Lecithin, 88 
Leucosin, 197 


M 


Malachite green, 184, 187 
Melting-points, determination of, 32 
Mercaptan, 125 
Mercuric thiocyanate, 125 
Metals, tests for, 38 
Metaproteins, 196 
Methane, preparation of, 43 
properties of, 44 
Methyl alcohol, 53 
-amine, 86 
-aniline, 151 
cyanide, 94 
iodide, 96, 97 
orange, 183 
salicylate, 53 
Milk, 199 
formaldehyde in, 81 
Millon’s reaction, 194 
reagent, 209 
Mixture, analysis, 206 
Molisch reaction, 115, 195 
Mordants, 187 
Mucic acid, 118 
Murexide test, 126 


N 


Naphthalene, 133 
Nicotine, 191 : 
Nitraniline, m, 177 
p, 178 
Nitranilines, salts of, 179 
Nitro-acetanilide, 178 
benzene, 135-137 
compounds, 135 
-phenol, o and p, 175 
Nitrogen, test for, 40 
test for in proteins, 192 


O 


Oils, 78 
emulsification of, 79 


214 INDEX 


Osazones, 116 

Oxalic acid, preparation of, 66 
properties of, 67 
tests for, 67 


P 


Paper, test of, 124 

Parchment-paper, 122 

Pentosans, 124 

Peptones, 197 

Perkin’s synthesis, 167 

Phenol, preparation of, 153 
properties of, 162 

Phenols, from sulphonic acids, 140 
reactions of, 163 

Phenyl-hydrazine, 157, 158 
-hydroxylamine, 137 
-semicarbazide, 158 

Phosphorus, test for, 41 
test for in proteins, 192 

Phthaleins, 163 

Potassium benzenesulphonate, 140 
cyanide, 92 
ethyl sulphate, 75 
ferric oxalate, 67 
ferricyanide, 93 
ferrocyanide, 93 
tetroxalate, 67 
thiocyanate, 125 
xanthate, 125 

Primuline, 187 

Proteins, analysis of, 192 
and formaldehyde, 82 
color reactions of, 194 
hydrolysis of, 196 
precipitation reactions of, 193 

Proteoses, 197 

Pyridine, 189 


Q 


Quinoline, 190 
Quinone, 172, 173 


8 


Saccharic acid, 118 


Salicylic acid, 179 
detection of in foods, 180 
Saliva, 120, 121 
Salting out of proteins, 196 
Sandmeyer reaction, 154 
Saponification, 64 
Schiff’s reagent, 208 
Schweitzer’s reagent, 122 
Silk, 200 
Silver oxalate, 68 
Skraup’s synthesis, 190 
Soap, 64 
Sodium, benzenesulphonate, 138 
manipulation of, 27 
Specific gravity, determination of, 
37 
Starches, 119, 120 
Sublimation, 23 
Succinic anhydride, 74 
Sucrose, 117 
Sugars, general properties of, 115 
Sulphanilic acid, 177 
Sulphonie acids, 138 
identification of, 140 
Sulphur, compounds, 125 
test for, 40 
test for in proteins, 192 


c 


Tartaric acid, 107-109 
Tannic acid, 180-182 

Tea, 127, 181 
Terephthalie acid, 168 
Textile fibers, 199 
Thermometers, calibration of, 31 
Thiocyanates, 125 
Thiophene, [89 

Tobacco, 191 

Tollen’s reagent, 208 
Toluenesulphonic acid, p, 141 
Toluic acid, p, 166 
Tolunitrile, p, 154 


‘Tribromphenol, s, 162 


Trichloracetic acid, 106 
Triphenylchlormethane, 146 
Triple bond, test for, 51 


INDEX 


U 
Unsaturated compounds, test for, 50 


Urea, 90, 91 
Uric acid, 126 


Verdigris, 63 
W 


Water, test for in organic compounds, 
55 


215 


Wheat, proteins of, 197 
Wool, 200 

— composition of, 195 
Wurtz synthesis, 45 


xX 


Xanthates, 125 
Xanthoproteic reaction, 194 


ry, 


Yield, calculation of, 2 














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